Ability to remove inputs from notebook cells in documentation

[mdbenito]

That. Use case: remove plotting or boilerplate code from the generated docs.

With nsbphinx it is possible to add the metadata "nbsphinx": "hidden" and hide both input and output, but this is not enough for e.g. plots, for which the plotting code is just noise in the documentation.

There are multiple issues in nbsphinx related to this, like e.g. spatialaudio/nbsphinx#15 or spatialaudio/nbsphinx#543 but all have been abandoned.

We could work on one of those PRs and get it merged. Alternatives?

[mdbenito]

This was fixed with the transition to mkdocs in 0.7.0