feat: open code block as modal

[ToBinio]

This PR makes it possible to add :modal to a code block.
This adds a button to the code block which makes it possible to open it in a "fullscreen"
modal.
This is useful for cases where the code is very wide and you would need to constantly scroll left and right to see the whole content.
example in the wip fabric wiki

[brc-dd]

Just a heads up though, <dialog> doesn't meet our browser support baseline. So it's unlikely this will be accepted any time soon.

[ToBinio]

I think it should still be easily doable without <dialog> it would just make the code a bit simpler

Thanks for the quick answer!