Add preview and split view to code block

[virgile-dev]

Is your feature request related to a problem? Please describe.
It's great to format code according to languages but if we are offering mermaid and LaTeX why don't we offer a display and splitview mode.

Describe the solution you'd like
What Notion did is pretty neat. They even have a syntax checker that displays errors

Capture.video.du.06-10-2025.17.01.43.webm

Describe alternatives you've considered
A clear and concise description of any alternative solutions or features you've considered.

Additional context
Add any other context or screenshots about the feature request here.

Bonus

• I'm a sponsor and would appreciate if you could look into this sooner than later 💖

[YousefED]

Thanks! Agree, would be great to work on this and provide a great foundational component for code-based blocks like mermaid, math, etc!

[woutervroege]

linking product goal TypeCellOS/Product#42