[CI] CI on master should automatically create releases

[citelao]

We probably want an action that runs on pushes to master that automatically creates a GitHub Release. https://github.com/actions/create-release exists but is deprecated; https://github.com/marvinpinto/action-automatic-releases looks good at first glance (though I haven't looked too deeply at the alternatives).

The artifacts that are published by our current checks are only retained for 90 days, and this cannot be prolonged. GitHub Releases are the true way to upload these files.

This will make the tool much easier to start using.

Follow-up from #31

[rsaxvc]

That sounds helpful. Is there any easy way to differentiate say, tagged releases from automatics? I assume they'd just have the same the previous commit used.

[citelao]

You can mark releases as "pre-release", so we can create automatic tags and automatic releases that are all "pre-releases." And then manually promote the releases we want.

I believe one of my old repos does something similar (though it uses Travis CI): https://github.com/citelao/Spotify-for-Alfred/releases