🌐 WebKit compatibility update :
- Restored WebKit compatibility following the latest Steam client update (Issue #157).
- Updated over 1,200 CSS class names that were changed by Steam.
- Restored the styling of numerous WebKit interface elements that had reverted to their default Steam appearance.
- Updated the affected WebKit customization options to work with the new Steam interface structure.
This major compatibility overhaul involved extensive updates across the theme to restore its visual consistency and ensure full compatibility with Steam's latest interface changes, justifying the version bump from 6.3.0 to 6.4.0.