Setup github actions

[jplehr]

We currently only run a CI pipeline for our internal repository.

We really should set up a github actions pipeline that runs the same tests for any opened pull requests.

Since we have a .gitlab-ci.yml file in place that lists what we do for testing, the setup should not be problematic. We need to consider however, that we probably want a container that can be used for theses tests, because building Score-P every time doesn't make sense.