Compile cross-platform binaries with GitHub Actions

[phiresky]

Windows, Linux, and MacOS binaries should be built via GitHub Actions.

This should happen whenever a new tag is pushed (e.g. for releases with cargo release) and possibly also "nightly" (the newest commit on master, at most once per day)

[phiresky]

"nightly" seems to not be trivial to do with GH Actions, so maybe just based on pushed tags is fine