message: Add Authentication section in Getting Started
  Closes
diff: @@ -58,6 +58,17 @@ yarn start
  That starts up the frontend on port 3000, and should automatically open a
  browser window showing it.
  +## Authentication
  +
  +When Backstage starts, you can choose to enter as a Guest user and start
  +exploring.
  +
  +But you can also set up any of the available authentication methods. The easiest
  +option will be GitHub. To setup GitHub authentication in Backstage, see
  +[these instructions](https://github.com/spotify/backstage/tree/master/plugins/auth-backend#github).
  +
  +---
  +
  Congratulations! That should be it. Let us know how it went
  [on discord](https://discord.gg/EBHEGzX), file issues for any
  [feature](https://github.com/spotify/backstage/issues/new?labels=help+wanted&template=feature_template.md)
  