This PR uses ruby/setup-ruby-pkgs, as ragel needs to be installed on Ubuntu & macOS platforms. Cross platform package installation is essentially the only reason for the action. It uses the code from ruby/setup-ruby for all the operations it performs.

The PR also adds all MRI head builds, including Windows mswin.

Rebased and updated - ubuntu-22.04, macos-12, Windows mswin

@MSP-Greg Sorry to request again. Can you rebase from master branch? I'd like to merge ruby/setup-ruby-pkgs@v1 and ragel installation changes.

@hsbt Done. I added workflow_dispatch, which can be helpful here or in forks for checking intermittent failures/errors, etc.

@hsbt A little off topic, but would a workflow that checks whether ext/json/ext/parser/parser.rl matches ext/json/ext/parser/parser.c be helpful? Puma has one, and it checks that any change to the *.rl is also done to the *.c file.

Or, it checks that ragel produces the commited c file from the commited rl file...

Regardless, it will be tomorrow at the earliest, 23:35 here.

diff checker of ragel is helpful. But https://github.com/puma/puma/blob/master/.github/workflows/ragel.yml seems too large for only checking. It may be hard to maintain in the future.