Added reverse op

pkg/yqlib/doc/operators/reverse.md

@@ -0,0 +1,48 @@
+# Reverse
+
+Reverses the order of the items in an array 
+
+{% hint style="warning" %}
+Note that versions prior to 4.18 require the 'eval/e' command to be specified. 
+
+`yq e <exp> <file>`
+{% endhint %}
+
+## Reverse
+Given a sample.yml file of:
+```yaml
+- 1
+- 2
+- 3
+```
+then
+```bash
+yq 'reverse' sample.yml
+```
+will output
+```yaml
+- 3
+- 2
+- 1
+```
+
+## Sort descending by string field
+Use sort with reverse to sort in descending order.
+
+Given a sample.yml file of:
+```yaml
+- a: banana
+- a: cat
+- a: apple
+```
+then
+```bash
+yq 'sort_by(.a) | reverse' sample.yml
+```
+will output
+```yaml
+- a: cat
+- a: banana
+- a: apple
+```
+