Important bug fixes and improvements release for Firefox 133.

• Fix some Firefox 133 leftovers
• Improve theme to better match GNOME 47
• Introduce gnomeTheme.allTabsButtonOnOverflow opt pref
• Introduce gnomeTheme.bookmarksOnFullscreen opt pref
• Make bookmarks bar more compact
• Use purple for private windows
• Initial theming for sidebar revamp
• Resolve some problems with right-to-left languages
• Add macOS compatibility to installation script (@cosmopool)
• Various theme improvements
• Bug fixes (@ricewind012)
• Code cleanup