oc: add README (#8188)

plugins/oc/README.md

+# OC - OpenShift CLI
+
+This plugin provides autocompletion for [OC](https://docs.openshift.com/container-platform/3.7/cli_reference/index.html) commands, building, managing and updating operations.
+
+To use it, add `oc` to the plugins array of your zshrc file:
+
+```bash
+plugins=(... oc)
+```
+
+## Contributors
+
++ [kevinkirkup](https://github.com/kevinkirkup) - Plugin Author