Draft: Set pydocstyle to google

Rationale:

• We don't use any style, just convention: null with some formatting rules.
• Textual uses such a style
• Pycharm correctly interprets it
• such a convention can be later used to auto-generate docs. See: https://textual.textualize.io/api/

E.g.

instead:

will be:

and instead:

will be: