On the Write documentation section, I couldn't find exactly how to get started easily.

I was able to find out what I need to do:

$ tox -e docs
$ firefox doc/en/_build/index.html

Then I could check my changes locally. I think it might be nice to add a note in the 'Writing documentation' section for those commands, especially for people not used to working with tox/sphinx/looking in the setup.cfg.

Or it's written somewhere else?

I'll submit a PR if that is useful 🍻