feat(mongo-atlas): add completion for atlas (#11349)

plugins/mongo-atlas/README.md

@@ -0,0 +1,10 @@
+# MongoDB Atlas plugin
+
+This plugin adds completion for [Atlas](https://www.mongodb.com/docs/atlas/cli/stable/) a command line interface built specifically for 
+MongoDB Atlas.
+
+To use it, add `mongo-atlas` to the plugins array in your zshrc file:
+
+```zsh
+plugins=(... mongo-atlas)
+```