Similar to the already patched `FormMixin`, the detail and list generic view classes are also missing __class_getitem__ and choke when you try to use their generics.
* run black
* create monkeypatching function for adding get_item dunder
* whoops i forgot the test
* change the name in INSTALLED_APPS to make test pass
* turn the whole thing into a proper package
* move django_stubs_ext to requirements.txt
* also install requirements.txt
* attempt to fix pre-commit
* numerous small code review fixes
* fix dependency issues
* small dependency fixes
* configure proper license file location
* add the rest of the monkeypatching
* use strict mypy
* update contributing with a note monkeypatching generics
* copy release script from parent package
