Update black in pre-commit and add blacken-docs.
Update black in pre-commit and add blacken-docs.

yougov/pmxbot,jaraco/backports.functools_lru_cache,jaraco/irc,pwdyson/inflect.py,hugovk/inflect.py,jaraco/jaraco.itertools,jaraco/zipp,yougov/pmxbot,jaraco/hgtools,jaraco/jaraco.context,jazzband/inflect,jaraco/jaraco.classes,yougov/pmxbot,jaraco/jaraco.stream,jaraco/tempora,python/importlib_metadata,jaraco/portend,jaraco/calendra,jaraco/jaraco.collections,pytest-dev/pytest-runner,jaraco/jaraco.path,jaraco/jaraco.functools,jaraco/jaraco.text,jaraco/keyring,jaraco/jaraco.logging