Fullscreen button for the "submit new dweet" area

[FireyFly]

Something I missed a few times when working on a new dweet is the ability to see how it behaves in fullscreen. This is especially true for interactive tweets, where tracking the mouse coordinate well might be a bit annoying in fullscreen currently. Would be great (and make sense) to have the "fullscreen" option for the "working area" too.

[lionleaf]

Fullscreen editing should behave something like http://arkt.is/t/ :)