Django-migrations-formatter

- Removed support for Python 3.6.

- Removed support for Django 3.0 and 3.1.

- A minimum version of `black>=22.1.0` is required.

- Added the `black` and `isort` installation extras. One can now automatically
install black and isort with `python -m pip install
"django-migrations-formatter[black,isort]"`.

* Add explicit support for Django 4.0 and Python 3.10

* Add explicit support for Django 3.2

* Another shot at a single-file GitHub workflow

* Fix release building

* Use [pre-commit.ci](https://results.pre-commit.ci/repo/github/351587462) for linting

* Use a single workflow file