General cleanup

[mdbenito]

This issue gathers some things that popped up after a cursory glance at the repo:

• Do not commit OS-specific junk to the repo #5
• Number notebooks #6
• Remove leftovers from the template #7
• Add a license file  #8
• Publish pages after build #10
• Use type hints for all functions #14

Finally, please always keep in mind that we want to publish the notebooks eventually. For that they have to be orders of magnitude better than your run-of-the-mill medium post or kaggle notebook. This not only involves designing good examples and doing a sound analysis but telling a story (I am aware that this is mostly done orally during the workshop, but maybe we can advance a bit in the direction of a playbook for the notebooks we have?), avoiding any typos, being consistent in the code, etc. The more work is done now, the less it will be before publication.