Revamp Color Theme and Docs/Features

[DogeDark]

This PR primarily revamps the use_preferred_color_scheme hook into use_system_theme.

Additionally, this PR features a few other things such as:

• Improved docs
• Feature name changes
• All tests passing!
• Fixes such as including the notification module (how did this get excluded?)
• Clippy fixes.
• And probably some more.

*Has breaking changes.

Closes #35