omit operator (#1989)

pkg/yqlib/doc/operators/omit.md

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+
+## Omit keys from map
+Note that the order of the keys matches the omit order and non existent keys are skipped.
+
+Given a sample.yml file of:
+```yaml
+myMap:
+  cat: meow
+  dog: bark
+  thing: hamster
+  hamster: squeak
+```
+then
+```bash
+yq '.myMap |= omit(["hamster", "cat", "goat"])' sample.yml
+```
+will output
+```yaml
+myMap:
+  dog: bark
+  thing: hamster
+```
+
+## Omit indices from array
+Note that the order of the indices matches the omit order and non existent indices are skipped.
+
+Given a sample.yml file of:
+```yaml
+- cat
+- leopard
+- lion
+```
+then
+```bash
+yq 'omit([2, 0, 734, -5])' sample.yml
+```
+will output
+```yaml
+- leopard
+```
+