Create .gitignore and Java CI with Gradle

[ItzSwirlz]

.gitignore: This ensures you don't push built binaries and stuff. You can put those in GitHub Releases

CI: Use GitHub Actions. You can test using multiple versions of Java (which you should) but for now I stuck with the default 1.8 and if you want to add several versions with a matrix strategy I can help you with that.

[mandar1jn]

@AffluentAvo why did you approve twice?

[mandar1jn]

Great pr. one thing I would request is that you use the upload artifact action so people can download the artifact instead of building it themselves