[CI] Linting of docs

[eddiebergman]

Currently there is no linter for doc and docstrings.

As a follow up, this should really be linted. I would advocate using ruff but theoretically that's blocked on still supporting python 3.6 (#1083).

Should work if working in an environment that's 3.7+ though.

The alternative is to use pydocstyle.

This would prevent issues like #716 from appearing. (which I guess can be closed now?)

[PGijsbers]

ruff is the way to go here I think. Since we want to drop 3.6 and fewer tools for the same functional behavior is better.