Add CI / CD

[mariobodemann]

Is your feature request related to a problem? Please describe.
Building the app currently is done while checking out the repository locally. Invest into automation of building: Using github actions to verify the state of the parser but also create github releases for every new APK.

Describe the solution you'd like
I'd love to be able to checkout a working app, without needing to recompile this repository by hand.

Describe alternatives you've considered
We could think about using #4, but for starters investing into building the basic CI/CD infrastructure should be good.

Additional context
Good first issue: This should be a self contained and simple task: It should be following best practices in creating github actions for building android apps.