Django-tailwind

- Makes `cookiecutter` dependency optional by installing it automatically when `python manage.py tailwind init` is run;
- Updates Django dev dependencies;

- Upgrades Tailwind CSS dependencies;
- Upgrades Django dependencies;

- Brings removed `browser-sync` snippet to support legacy configs;
- Follow [migrating from `browser-sync` to `django-browser-reload`](./docs/django_browser_reload.md) instructions if you've upgraded.

- Replaces `nodemon` and `browser-sync` with `django-browser-reload`;
- Deprecates `TAILWIND_DEV_MODE` setting, the development mode now is deemed when `DEBUG=True`;
- Updates *Tailwind CSS* dependencies to their latest versions;
- Removes `--no-sync` flag for `python manage.py tailwind start` command;

- Fixes minimum Django version requirement. Sets it back to `2.2`.

- Upgrades project template to be compatible with Tailwind CSS `v3.0`;
- Drops Tailwind CSS `v2.x` support;
- If you're not starting fresh, [follow the upgrade guide](https://tailwindcss.com/docs/upgrade-guide) to upgrade existing Tailwind CSS `v2.x` to `v3.x`;