ThemeManager planned improvements, feedback wanted

Hi,

I would like to become a main contributor/maintainer for this project.

Contribution Ideas:

1. Update demo project (maybe add to mublazor docs)
2. Add more options (upcoming skeleton color for example: https://github.com/MudBlazor/MudBlazor/pull/9815)
3. Add presets (Default, pastel, neon,...)
4. Ability to load custom fonts
5. Exporting/importing themes (See #3)
6. Improve readme
7. Performance/stability
8. Diagnostics (warnings for accessibility and contrast for example)
9. Add tests
10. Make things more compact overall (dense/margin) to be able to show as many things as possible on demo page.

Would like to discuss these further here with the community.