Check auth tokens for Actions

[Kade-N]

Need to check the following to ensure actions workflows can run reliably and securely

• correct access to Updater repo
• adding token to app so it can access GH API

This appears to be the cause of failing build action right now

Also include instructions in readme for adding own token for API integration (and review #116 so we can support the token being missing)

[Kade-N]

Added a new token to access the Updater repo and trigger its actions workflow, although it would be nice if we can eliminate the need for this altogether

Build action workflow is working now

The actual app token is still the old one, we don't need to replace it immediately but would be good to bring it into this org. Still need to add instructions for custom app token, as well as support no token.