Consider moving the examples out of the Blackjax repo

[rlouf]

I several main advantages:

• Reduce CI time in blackjax, and allow for longer notebook runs.
• Independent development
• Self-contained reference on sampling methods

This example repo would render the notebook in CI and display them with Executable Books. We could expand the repo with tutorials that are algorithm-specific, and add comparisons between algorithms on similar models. We could probably improve the CI to only run modified notebook, thus allow for longer runs.

It would eventually read as a nice book on sampling methods.