Django-simple-menu

- Fixed generation of documentation on ReadTheDocs

- Fix generation of version number using setuptools_scm which prevented a

- BREAKING: dropped support for Python < 3.6
- BREAKING: dropped support for Django < 3.2
- DEPRECATION: the module is now called "simple_menu" instead of "menu" (93)
- BREAKING: when using "simple_menu", the Bootstrap templates are located
inside the "simple_menu" subfolder
- Moved CI to GitHub Actions (67, 72)
- Project is now a part of Jazzband (54)
- Updated the example app

- Fixing sdist packaging

- Require Django 1.6+ now (this is because we now use slugify instead of a regex)
- Ensure thread safety 42
- Allow complex checks to be built by subclassing MenuItem 43

- Fix bug introduced in 1.1.1 surrounding child sorting 38
- Improve tests