tests: Add task to run tests, add github workflow to run task

[marcusramberg]

You can see how the test run looks on my fork - https://github.com/marcusramberg/nimdow/actions/runs/5136120902/jobs/9242453480

[avahe-kellenberger]

I actually have nimtest as a dependency here, we can simple run the nimtest executable to run all the tests :slightly_smiling_face:

[marcusramberg]

Nice, I wasn't even aware nimtest is a thing. That's a lot easier 💯