Update notebook table and transformers intro notebook
# What does this PR do?

Update the examples table and the notebooks table to include all recent examples. Also fix the intro notebook to the transformers library, in particular, the image that was missing.

Fixes #9083

Discussion on pinning/testing notebooks needs to be global on all notebooks (not just one) so merging this for now. We can think of a strategy and implement it in a follow-up PR.