- Add black and isort for Python styling
- Add doc8 for reStructuredText styling
- Add prettier for css/html/js/md/yaml styling
- Run all styling tools from pre-commit hooks
- Adjust flake8 config for compatibility with black
(and current Django style)
- Add some other helpful pre-commit hooks
- Update editorconfig to match Django
(with a few necessary adjustments for Anymail)
- Update `tox -e lint` to run all pre-commit hooks
- Update contributing docs
