Enable external contributions would be helpful

I did not notice that it was limited (might be an extra case for #149) and got a PR ready for the initial setup and onboarding improvements:

https://github.com/githubnext/chopin/compare/main...rajbos:github-vnext-chopin:main?expand=1

Let me know if you want it 😄

Start with the compare link in the issue and review the proposed initial-setup and onboarding changes. Confirm which repository setting or project changes are needed to accept external contributions, then verify that a newcomer can follow the onboarding path and open a contribution.

Written by the indexing model from the issue text.