Make simple CI testing if notebooks are running to the end

[agoscinski]

Hello, because we probably will need to change the notebook still quite a few times, it would be useful to have some automatic tests for a PR, just to check if the notebooks are running at all. Checking the functionalities is a different story and requires more work and thinking, but just having a simple automatic test running the notebooks I think would be worth the effort. @victorprincipe mentioned that he would be interesting in it. @ceriottm what do you think?

[ceriottm]

Sounds like a good idea, but I don't think it's urgent. Something that could help and may be easier is a "check all" function. Putting reference answers in the CI is a problem imo.