Add zen mode reading feature

Hello,

Could be nice to add add zen mode reading feature:

you could click the Zen mode icon to hide sides and header navigation and only display the page content: like ?xpage=plain&htmlHeaderAndFooter=true URL query settings.

The zen mode also activates the browser’s full-screen mode too.

https://forum.xwiki.org/t/brainstorming-xwiki-11-x-cycle-roadmap/3979/40

ty

Pascal