Django-icons

- Switch to a CalVer YY.MINOR versioning scheme. MINOR is the number of the release in the given year. This is the first release in 2021 using this scheme, so its version is 21.1. The next version this year will be 21.2. The first version in 2022 will be 22.1.
- Add support for Django 4 and Python 3.10 (193).

- Set `IconRenderer` as default renderer (58).
- Defer evaluation of strings (53).
- Stop using `mark_safe` (57).
- Merge `extra-classes` (55).
- Fix example app (49).
- Rename `FontAwesomeRenderer` to `FontAwesome4Renderer` (48).
- Fix PyPI description.
- Fix PyPI classifiers.

- Add Dependabot.
- Revert to setuptools for packaging.
- Drop support for Django 3.0, extended support stopped on 2021-04-01).
- Add support for Django 3.2.

- Update dependencies.
- Reformat CHANGELOG.
- Add docs and tests to sdist.
- Use GitHub Actions for CI.
- Use production version of Django 3.1 in tox matrix.

- Add support for Python 3.9.
- Use build system poetry-core instead of poetry.
- Accept importlib-metadata 2.x.x.
- Update test settings to prevent Django 3.1 warning.
- Replace `m2r` with `m2r2` to support Sphinx3.

- Remove dependency on sphinx_rtd_theme (fixes 21).