Set up CI (works on Linux, macOS, and Windows)

I think there aren't much Windows users but I think is good mentioning it. https://github.com/jcs090218/setup-emacs is combination of the following two actions, * https://github.com/purcell/setup-emacs (Linux and macOS) * https://github.com/jcs090218/setup-emacs-windows (Windows) Hope people find it useful!

X has been shitty for me this morning (something about changing my hostname made it so my crontab that opens my zoom standup needs to be run twice). It's annoying, but now I'm just happy that I'm not on windows, so thanks! ;)