Playground Enhancements

[shai-almog]

1. Fix dark mode especially in side menu and tabs - Done
2. Download project button - Done
3. Live CSS editor - Done
4. Fix playground on mobile devices - Done
5. Tutorial trail mode - Moved this to a separate issue
6. Disable swipe on side menu - Done
7. Support missing Java features from BSH:* For loops on arrays

• Method references
• Inner classes
• etc.

[shai-almog]

Implemented CSS editor in #4649