Added line and column operators

pkg/yqlib/doc/operators/line.md

@@ -0,0 +1,68 @@
+# Line
+
+Returns the line of the matching node. Starts from 1, 0 indicates there was no line data.
+
+{% hint style="warning" %}
+Note that versions prior to 4.18 require the 'eval/e' command to be specified. 
+
+`yq e <exp> <file>`
+{% endhint %}
+
+## Returns line of _value_ node
+Given a sample.yml file of:
+```yaml
+a: cat
+b:
+  c: cat
+```
+then
+```bash
+yq '.b | line' sample.yml
+```
+will output
+```yaml
+3
+```
+
+## Returns line of _key_ node
+Pipe through the key operator to get the line of the key
+
+Given a sample.yml file of:
+```yaml
+a: cat
+b:
+  c: cat
+```
+then
+```bash
+yq '.b | key| line' sample.yml
+```
+will output
+```yaml
+2
+```
+
+## First line is 1
+Given a sample.yml file of:
+```yaml
+a: cat
+```
+then
+```bash
+yq '.a | line' sample.yml
+```
+will output
+```yaml
+1
+```
+
+## No line data is 0
+Running
+```bash
+yq --null-input '{"a": "new entry"} | line'
+```
+will output
+```yaml
+0
+```
+