Create an onboarding doc that can be used to help set up environments for plugin testing.

Meant to be an evolving doc that will be updated as we add / remove plugins from the list. It will capture the following:

• List of plugins that we currently supporting 
• A link to a video on how to configure the plugin for testing
• Version of Backstage / RHDH / plugin that the video is based on

Goal would be to convert this Google doc to techdocs for our team instance to share with the rest of the team. Ideally, we should also encourage others to update whenever a video becomes out of date.