[Feature Request] Actions: `on:` directive: of another repo

So mostly forks, it’d be neet if I could do this:

on:
  push:
    repo: github.com/jtagcat/jtagcat
    branches:
      - main
  release:
    repo: jtagcat/jtagcat
    types:
      - published

Bonus points for working not only on GitHub as well, but it’s likely ‘initial release only for gh’, and low-priority stale for ‘other hostlings’. At least try to make it easier to add support for everything else, ok?