I inadvertedly broke the documentation by adding the cssselect module. Sorry for that.
This gave me the opportunity to overhaul the look of the documentation, it now has the familiar style of ReadTheDocs, which is IMO much easier to read than the default sphinx style.
It now looks like this: https://joneuhauser.gitlab.io/-/extensions/-/jobs/1274341705/artifacts/build/sphinx/html/index.html
It seems like Numpy/Google-tyle docstrings are more often used than rst docstrings. Therefore the extension "napoleon" was loaded. We should definitely proofread these generated pages though. Note that I haven't gotten type linking to work with "napoleon" yet, so it might make sense to homogenize the docstrings into sphinx format.
A stub landing page has been added as well, so it's clear how additional documentation can be added.
I suggest pinging the author of https://gitlab.com/binyamin/inkscape-extensions-guide whether his work can be transferred to the project repository.