Add popup preview support to the block editor

[marklchaves]

Describe the feature request

I'd like to see a Preview button in the block editor when you turn on block editor support. This Preview button should work just like the one for the classic editor.

Use case

So you can see a "live" preview of the popup you're building just like when you edit a popup with the classic editor.

Example screenshots (if any)

[m1ga]

Would be great to have that so we can use the Block Editor. Even a "Preview" option in the "all popups" table next to "edit" would already be helpful.