Documentation list in readme.rst is not up to date

[rfl-urbaniak]

Every time a new document is added, the list of documents in readme.rst needs to be updated manually. At minimum, it needs to be updated; optimally, some way of updating the list automatically would be great.

[eb8680]

Automation is nice when it works (see e.g. sphinx-gallery), but I'm not sure it's worth the effort to do anything beyond reminding future reviewers that any PR adding a new example should also add it to Sphinx. It's not like we're adding these things at a blistering pace. Maybe there's a linter feature or Sphinx option that would cause docs builds to fail if there is a dangling notebook?