Fix Main Menu showing up as white

- Fix submit confirmation and skip to main content background color being white
- Fix quick links hover color
- Fix app menu icon color when the viewport is small

- Fixed Classes banner being white
- Improve Announcement and sub menu's dark theme
- Fixed background color when dragging class cards
- Fixed hover color for submenus
- Correction of “More actions” menu in attachment preview screen
- Corrected “Open with” menu in attachment preview screen
- Fixed background color of tooltips
- Fixed overhang of diagonal line in archived classes
- Fixed some Japanese localization

- Fix help button background
- Fix active tab hover
- Fix comment mentions
- Fix comment formatting buttons
- Fix tab hover
- Fix classwork border-color

- Fix CSS issues when hovering and teacher-side dark mode
- Minor documentation changes

* Fix CSS for the main menu, loading bar, and more
* Compress extension icons
* Run content scripts (CSS injection) at document start
* Update content script match URLs

- Add localization for listing description
- Add Firefox and Opera
- Fix hovering in Classwork
- Fix Firefox not having proper permissions
- Update translations
- Minor changes