ci: add scripts for trusting PRs from forks to allow CI to run

[trevor-coleman]

Please verify the following:

• yarn build-and-test:local passes
• I have added tests for any new features, if relevant
• README.md (or relevant documentation) has been updated with your changes

Describe your PR

Summary

• adds the ci:trust script and related docs. to the local repo
• CircleCI Changes:
  • add the "trust-check" step, to ensure CI doesn't run on untrusted forks
• Adds github workflows to:
  • push PR changes to a trusted branch then clean up automatically after 2h
  • delete all temp trusted branches with matching branch names

Notes:

• Based on this article, this config prevents the build-docs action from running on untrusted forks.
• CI will check if a branch is trusted before running CI
• Once a branch is trusted, then CI will run
• The github workflow to create a temp branch will automatically clean up the branch after a couple hours, and a separate action is provided to manually delete all temp branches in case any get left behind.
• the ci:trust script will need to be cleaned up manually for now -- can maybe automate that with a cron job in github workflows

[joshuayoes]

I gave this a test on #1466 and it works ✅