Automate release and move away from Travis CI

[ysb33r]

I suggest that whilst keeping the source on GitHub we utilise the GH Actions support to be able to automate builds and also automate the release process.

We need to

• Add the appropriate GH workflow
• Add a section that will auto-release if anything is merged to a release branch.
• Protect the release branch on GitHub

[rtyler]

@ysb33r I have experimented a bit with GitHub Actions in other projects, would that be a workable fit?

[ysb33r]

@rtyler Let's give Actions a go first.

[ysb33r]

@rtyler Thanks. I've added the first GH actions, now just have to add the job for publishing and modify gradle build accordingly