* blacken-docs: Manual fixes for command to pass without errors
* blacken-docs: Adds blacken-docs step to precommit hook.
* blacken-docs: Adds changes made by command itself.
* blacken-docs: Modifies blacken-docs step to only process files under "docs" directory
* blacken-docs: Updates pre-commit config file to exclude all directories other than "docs" to be compatible with "--all-files" flag.
* blacken-docs: Adds commas at the end to make it look identical to pre-black version
This fixes recent issues with installing isort via pre-commit that was
introduced in recent versions of poetry-core.
See https://github.com/PyCQA/isort/pull/2078
