Introduce pre-commit

[hartwork]

…so that CI and developers can run the very same QA checks and things stay clean.

pre-commit is up here and kicks ass. To give it a try as a Git pre-commit hook locally:

git clone --branch introduce-pre-commit https://github.com/hartwork/django-easy-select2
cd django-easy-select2
virtualenv --python=python3.7 py37
source py37/bin/activate
pip install pre-commit
pre-commit install --install-hooks

Prior to activation, you can see the very same GitHub Action over here:
https://github.com/hartwork/django-easy-select2/actions

[coveralls]

Coverage remained the same at 100.0% when pulling 801cc6d on hartwork:introduce-pre-commit into bc84f73 on asyncee:master.

[coveralls]

Coverage remained the same at 100.0% when pulling 801cc6d on hartwork:introduce-pre-commit into bc84f73 on asyncee:master.

[hartwork]

I'd be happy to discuss this pull request. Any thoughts?

[asyncee]

Sorry for delay, lgtm. Thank you!

[asyncee]

Would you like to become a collaborator?