Django-actual-admin-docs

- Removed 'highlight' extras marker. If `pygments` is installed, code blocks are highlighted, and if not, then not.

- Sample documentation for testing purpose is now part of the module.
- Added testing with docs.

- Improved local test setup,
- Index files are consistently recognized in subfolders.
- Pygments as a dependency is now optional.

- Added syntax highlighting for fenced code blocks.
- Added Pygments as a dependency.

- Initial version.