add publish configuration for github

[TheElan]

Part of: https://github.com/SinTh0r4s/ExampleMod1.7.10/issues/48

[TheElan]

It publishes to github maven repo, however there are two downsides I see now:

• you need to configure repository per artifact (e.g. maven url for this project looks like https://maven.pkg.github.com/SinTh0r4s/ExampleMod1.7.10)
• repository requires auth, which means you need to provide a user name and password when declaring repository. Since it's OSS repo any credential might be sufficient (as in CI should be able to pull things with it's token) and user could have them specified somewhere in environment/secrets files

[TheElan]

I also didn't found any way to remove artifacts from repo, probably you can't do this intentionally.