Slice array (#1403)

pkg/yqlib/doc/operators/slice-array.md

@@ -0,0 +1,77 @@
+
+## Slicing arrays
+Given a sample.yml file of:
+```yaml
+- cat
+- dog
+- frog
+- cow
+```
+then
+```bash
+yq '.[1:3]' sample.yml
+```
+will output
+```yaml
+- dog
+- frog
+```
+
+## Slicing arrays - without the first number
+Starts from the start of the array
+
+Given a sample.yml file of:
+```yaml
+- cat
+- dog
+- frog
+- cow
+```
+then
+```bash
+yq '.[:2]' sample.yml
+```
+will output
+```yaml
+- cat
+- dog
+```
+
+## Slicing arrays - without the second number
+Finishes at the end of the array
+
+Given a sample.yml file of:
+```yaml
+- cat
+- dog
+- frog
+- cow
+```
+then
+```bash
+yq '.[2:]' sample.yml
+```
+will output
+```yaml
+- frog
+- cow
+```
+
+## Slicing arrays - use negative numbers to count backwards from the end
+Given a sample.yml file of:
+```yaml
+- cat
+- dog
+- frog
+- cow
+```
+then
+```bash
+yq '.[1:-1]' sample.yml
+```
+will output
+```yaml
+- dog
+- frog
+```
+