Add the possibility to display in a full view page the page builder blocks editing

Steps :

Install a clean version of Ibexa 4.2

Create or edit an existing landing page

Drag and drop a text bloc click on block settings and fill the content with text. 

You notice that the block is stuck on the down right of the window.

The customer would have an option in a yaml file that allow to display this in a full screen/page view mode.