Setup Github Actions CI

[zealot128]

To avoid problems in the future :)

I made a basic Ruby Workflow. For that to work, I had to modify the gemspec to avoid loading Rake here.

You can see my fork's action runs: https://github.com/pludoni/ruby-secretariat/actions

• Using rake in Gemspec leads to errors, as Rake is not installed by default, so I replaced the FileList with the default stuff bundle gem generates
• Chose 3 Ruby versions to test, 3.2.2 could be dropped or changed to newer 3.2 release - that was just the default stuff that the Action Wizard put in there with a pinned setup-ruby action...

[halfbyte]

Hah, you beat me to it. I am not super happy with the git-ls usage, simply because there's some stuff we don't really need in the gem, but I've been stumbling over the exact same thing. I'll see if I can come up with something slightly more selective easily.

EDIT: Again, I'm too stupid or lazy to properly read the code. Sorry about that. I've merged my version with a minimal FileList replacement written in Ruby, just because I like it better than shelling out to git ls-files. Also slightly different selection of ruby versions.

Thanks for the effort though!