use case: testing example notebooks

[edublancas]

Many libraries have sample notebooks as examples. We can use nbsnapshot + ploomber for this.

I found this framework we can use for testing: https://github.com/pyannote/pyannote-audio

We're currently blocked by https://github.com/ploomber/ploomber/issues/950 - once that's finished, we can work on a complete end-to-end example that: 1. runs example notebooks in parallel with ploomber and 2. tests them with nbsnapshot.

we can add the example here: https://github.com/ploomber/notebooks-ci