Automatically test python code in the documentation

[RemiLehe]

We have several examples of Python code in the documentation:

• Tutorials: https://lasydoc.readthedocs.io/en/latest/user_guide/index.html This could be replaced by a Jupyter notebook, that gets incorporated in the doc, and automatically tested in the CI

• Code in docstrings: https://lasydoc.readthedocs.io/en/latest/api/profiles/gaussian.html This could be automatically tested with doctest (as part of our Github actions)

[ax3l]

For the 2nd part, we could even run doctests from pytest: https://stackoverflow.com/a/73456441/2719194