- split jobs into build/test/deploy
- test package on both macOS Intel and Apple Silicon
- cleanup some argument handling
- use `HOMEBREW_MACOS_OLDEST_SUPPORTED` naming to be consistent with
`brew.sh`
- note in `brew.sh` that `Distribution.xml` also needs updated (and do
so)
- various other little bits of style cleanup
- don't include GitHub Actions credentials
- generate and include RTF version of Homebrew BSD license
- create nicer installer with `productbuild`
- customise welcome/conclusion messages
- add Homebrew logo as a background image
- remove unnecessary `preinstall` script
- cleanup `postinstall` script to pass `brew doctor`
- use `Distribution.xml` for a nicer installer
- require CLT or Xcode rather than using our hacks to try and install
CLT during installation