Publish to a proper package repository

[AlvaroBrey]

JitPack is highly convenient as it takes very little effort but it comes with some drawbacks:

• As its name implies, it only builds a version when somebody requests it. This means the first build with a new version either takes longer or just fails until it's built.
• Stability has not been the best as of late, with builds randomly failing because of JitPack server errors, and dependencies sometimes not being available.
• Additionally the web UI is clunky so it's fairly hard to debug what's wrong and to fix possible problems.

Moving forward, we should try to actively publish the library to a normal package repository. Obvious options are Maven Central and Github Package Registry.

This would of course require that we handle the build and push, but that can probably be accomplished in a simple way with Github Actions.