Test tutorials in CI

[EwoutH]

The tutorials are currently not tested in CI, as can be seen by that the visualization_tutorial.html is now broken because we removed the schedulers from the example models (in projectmesa/mesa-examples#183).

So, aside from the examples, the tutorials should also be tested in CI.

[EwoutH]

The bigger question is: Readthedocs is building this stuff. Why isn't it failing?

[EwoutH]

Two approaches on this:

• Add pytest script and CI job to test tutorials #2275
• Readthedocs: Don't let notebook failures pass silently #2276

For #2276, waiting on an upstream question. If that get's answered, #2275 might not be needed.