Add a CI pipeline using github actions

[D4N]

It would be nice to have a CI pipeline using Github actions that at least builds the extension on every commit & PR. Eventually it would be also nice to have some tests, but I am not sure how feasible that is.

It should be possible to steal most of the CI pipeline from the open build service connector: https://github.com/SUSE/open-build-service-connector

[m1-key]

@D4N Can we use Travis CI?

[D4N]

I'd prefer to avoid Travis, as their recent pricing changes made the usage as a non-paying customer quite inconvenient. Plus github actions involve a lot less magic.

[Abhirup-99]

@m1-key are you still working on this issue?