Following `Contributing.md` Leads to Failed Tests and Build

[jpjon]

Following the Contributing.md file, I get build and test errors after creating a shell with

rye sync

Follwing this directly from the file:

Python: Run mkdocs in one of the tests configurations:

• cd mkdocs_jupyter/tests/mkdocs/
• mkdocs serve -f material-with-nbs.yml

also results in an error.

The error, which also occurs when running pytest, is as follows:

jinja2.exceptions.TemplateNotFound: mkdocs_html/assets/index.css

[danielfrg]

I just tried with no issues. You need to also run the JS section.