Maximize link on description mess up the editor

The root cause of this issue is that the ExtensionSheet puts textarea as siblings of some content of the sheet providing other content explanation, without having a dedicated wrapper around the textarea. And the script in fullscreen.js responsible for handling the fullscreen is currently using the parent of the textarea to put the elements in absolute position for creating the fullscreen. So the simplest fix is to only provide a wrapper for the textarea that are messing up the sheet: providing a generic fix in fullscreen.js is not easy as dynamically inserting a wrapper around the textarea might mess up with other mechanism such as CodeMirror which also inject elements in the DOM and notably another textarea...