3.5.0-rc.4

All the good stuff from:

• https://github.com/getkirby/kirby/releases/tag/3.5.0-rc.1
• https://github.com/getkirby/kirby/releases/tag/3.5.0-rc.2
• https://github.com/getkirby/kirby/releases/tag/3.5.0-rc.3

and …

Enhancements

• Nested blocks are no longer broken
• Better image snippet with support for external images
• More unit tests
• Better debouncing of input events to increase performance
• Support for all 6 heading levels in the heading block
• Missing fieldset definitions are now handled more gracefully
• Group labels can now be translated