docs: enhance SSH configuration documentation and testing

- Replace detailed SCP and SSH proxy settings with a table format for better readability
- Improve clarity and grammar in instructions for creating and using SSH keys

Signed-off-by: appleboy <appleboy.tw@gmail.com>

README.md

@@ -4,7 +4,7 @@
 
 [![Actions Status](https://github.com/appleboy/scp-action/workflows/scp%20files/badge.svg)](https://github.com/appleboy/scp-action/actions)
 
-**Important**: Only support **Linux** [docker](https://www.docker.com/) container.
+**Important**: Only supports **Linux** [docker](https://www.docker.com/) containers.
 
 ## Usage
 
@@ -14,7 +14,6 @@ Copy files and artifacts via SSH:
 name: scp files
 on: [push]
 jobs:
-
   build:
     name: Build
     runs-on: ubuntu-latest
@@ -35,46 +34,50 @@ jobs:
 
 See the [action.yml](./action.yml) file for more detail information.
 
-* host - scp remote host
+| Variable            | Description                                                                                                 | Default Value |
-* port - scp remote port, default is `22`
+| ------------------- | ----------------------------------------------------------------------------------------------------------- | ------------- |
-* username - scp username
+| host                | SCP remote host                                                                                             | -             |
-* password - scp password
+| port                | SCP remote port                                                                                             | `22`          |
-* passphrase - the passphrase is usually to encrypt the private key
+| username            | SCP username                                                                                                | -             |
-* protocol - The IP protocol to use. Valid values are `tcp`. `tcp4` or `tcp6`. Default to `tcp`.
+| password            | SCP password                                                                                                | -             |
-* fingerprint - fingerprint SHA256 of the host public key, default is to skip verification
+| passphrase          | The passphrase is usually used to encrypt the private key                                                   | -             |
-* timeout - timeout for ssh to remote host, default is `30s`
+| protocol            | The IP protocol to use. Valid values are `tcp`, `tcp4`, or `tcp6`.                                          | `tcp`         |
-* command_timeout - timeout for scp command, default is `10m`
+| fingerprint         | Fingerprint SHA256 of the host public key. Default is to skip verification                                  | -             |
-* key - content of ssh private key. ex raw content of ~/.ssh/id_rsa
+| timeout             | Timeout for SSH to remote host                                                                              | `30s`         |
-* key_path - path of ssh private key
+| command_timeout     | Timeout for SCP command                                                                                     | `10m`         |
-* target - target path on the server, must be a directory (**required**)
+| key                 | Content of SSH private key. e.g., raw content of ~/.ssh/id_rsa                                              | -             |
-* source - scp file list (**required**)
+| key_path            | Path of SSH private key                                                                                     | -             |
-* rm - remove target folder before upload data, default is `false`
+| target              | Target path on the server, must be a directory (**required**)                                               | -             |
-* strip_components - remove the specified number of leading path elements.
+| source              | SCP file list (**required**)                                                                                | -             |
-* overwrite - use `--overwrite` flag with tar, overwrite existing files when extracting
+| rm                  | Remove target folder before uploading data                                                                  | `false`       |
-* tar_tmp_path - temporary path for tar file on the dest host
+| strip_components    | Remove the specified number of leading path elements                                                        | -             |
-* tar_exec - path to tar executable on the dest host. default is `tar`
+| overwrite           | Use `--overwrite` flag with tar, overwrite existing files when extracting                                   | -             |
-* tar_dereference - use `--dereference` flag with tar, follow symlinks; archive and dump the files they point to
+| tar_tmp_path        | Temporary path for tar file on the destination host                                                         | -             |
-* use_insecure_cipher - include more ciphers with use_insecure_cipher (see [#15](https://github.com/appleboy/scp-action/issues/15))
+| tar_exec            | Path to tar executable on the destination host                                                              | `tar`         |
+| tar_dereference     | Use `--dereference` flag with tar, follow symlinks; archive and dump the files they point to                | -             |
+| use_insecure_cipher | Include more ciphers with use_insecure_cipher (see [#15](https://github.com/appleboy/scp-action/issues/15)) | -             |
 
 SSH Proxy Setting:
 
-* proxy_host - proxy host
+| Variable                  | Description                                                                                                 | Default Value |
-* proxy_port - proxy port, default is `22`
+| ------------------------- | ----------------------------------------------------------------------------------------------------------- | ------------- |
-* proxy_username - proxy username
+| proxy_host                | Proxy host                                                                                                  | -             |
-* proxy_password - proxy password
+| proxy_port                | Proxy port                                                                                                  | `22`          |
-* proxy_protocol - The IP protocol to use. Valid values are `tcp`. `tcp4` or `tcp6`. Default to `tcp`.
+| proxy_username            | Proxy username                                                                                              | -             |
-* proxy_passphrase - the passphrase is usually to encrypt the private key
+| proxy_password            | Proxy password                                                                                              | -             |
-* proxy_timeout - timeout for ssh to proxy host, default is `30s`
+| proxy_protocol            | The IP protocol to use. Valid values are `tcp`, `tcp4`, or `tcp6`.                                          | `tcp`         |
-* proxy_key - content of ssh proxy private key.
+| proxy_passphrase          | The passphrase is usually used to encrypt the private key                                                   | -             |
-* proxy_key_path - path of ssh proxy private key
+| proxy_timeout             | Timeout for SSH to proxy host                                                                               | `30s`         |
-* proxy_fingerprint - fingerprint SHA256 of the host public key, default is to skip verification
+| proxy_key                 | Content of SSH proxy private key                                                                            | -             |
-* proxy_use_insecure_cipher - include more ciphers with use_insecure_cipher (see [#15](https://github.com/appleboy/scp-action/issues/15))
+| proxy_key_path            | Path of SSH proxy private key                                                                               | -             |
+| proxy_fingerprint         | Fingerprint SHA256 of the host public key. Default is to skip verification                                  | -             |
+| proxy_use_insecure_cipher | Include more ciphers with use_insecure_cipher (see [#15](https://github.com/appleboy/scp-action/issues/15)) | -             |
 
 ## Setting up a SSH Key
 
-Make sure to follow the below steps while creating SSH Keys and using them.
+Make sure to follow the steps below when creating and using SSH keys.
-The best practice is create the SSH Keys on local machine not remote machine.
+The best practice is to create the SSH keys on the local machine, not the remote machine.
-Login with username specified in Github Secrets. Generate a RSA Key-Pair:
+Log in with the username specified in GitHub Secrets and generate an RSA key pair:
 
 ```bash
 # rsa
@@ -108,9 +111,9 @@ See the detail information about [SSH login without password](http://www.linuxpr
 
 **A note** from one of our readers: Depending on your version of SSH you might also have to do the following changes:
 
-* Put the public key in `.ssh/authorized_keys2`
+- Put the public key in `.ssh/authorized_keys2`
-* Change the permissions of `.ssh` to 700
+- Change the permissions of `.ssh` to 700
-* Change the permissions of `.ssh/authorized_keys2` to 640
+- Change the permissions of `.ssh/authorized_keys2` to 640
 
 ### If you are using OpenSSH
 
@@ -149,6 +152,20 @@ Copy file via a SSH password:
     target: your_server_target_folder_path
 ```
 
+Using the environment variables
+
+```yaml
+- name: copy file via ssh password
+  uses: appleboy/scp-action@v0.1.7
+  with:
+    host: ${{ env.HOST }}
+    username: ${{ env.USERNAME }}
+    password: ${{ secrets.PASSWORD }}
+    port: ${{ env.PORT }}
+    source: "tests/a.txt,tests/b.txt"
+    target: ${{ env.TARGET_PATH }}
+```
+
 Copy file via a SSH key:
 
 ```yaml
@@ -208,7 +225,7 @@ Example configuration for exclude custom files:
 Upload artifact files to remote server:
 
 ```yaml
-  deploy:
+deploy:
   name: deploy artifact
   runs-on: ubuntu-latest
   steps:
@@ -273,7 +290,7 @@ foobar
 Only copy files that are newer than the corresponding destination files:
 
 ```yaml
-  changes:
+changes:
   name: test changed-files
   runs-on: ubuntu-latest
   steps: