ci: automate releases

[matejchalk]

Will hopefully close #48. Needs to be tested after merging. 🤞

I've replicated the releases setup from code-pushup/cli.

• Copy/pasted release.yml and publish.yml with only minor changes.
  • Used the latest actions/* versions. For create-github-app-token, this required switching from the deprecated app-id to a client-id.
  • Omitted NX_CLOUD_ACCESS_TOKEN, since this repo doesn't use Nx Cloud for now.
  • Minimized release.yml permissions as per CodeQL warning.
• Connected GitHub Actions as a trusted publisher for both packages on npmjs.com, disabled tokens.
  
• In GitHub repo settings:
  • Added repository variable and secret for the Code PushUp bot GitHub App.
    
    
  • Created a ruleset to allow the Code PushUp bot to push to main.
    
  • Created a release environment.