Leave fullscreen editor when displaying "Upload File" and "Meme" dialogs
Summary:
When being in fullscreen editor mode, the `Upload File` and `Meme` dialogs get opened behind the editor and thus are invisible.
Given the options listed in https://secure.phabricator.com/T8200, pop out of fullscreen when these buttons get clicked, as this is easiest to implement.
Closes T15901
Test Plan:
1. Go to any item which allows commenting, e.g. a task.
2. In the toolbar of the textarea, click the `Fullscreen Mode` button.
3. Click the `Upload File` or `Meme` button in the toolbar.
4. Check if the dialog is displayed.
6. Repeat the test in normal mode (not "Fullscreen mode") and see that it still works.
Reviewers: O1 Blessed Committers, valerio.bozzolan
Reviewed By: O1 Blessed Committers, valerio.bozzolan
Subscribers: avivey, tobiaswiese, valerio.bozzolan, Matthew, Cigaryno
Tags: #remarkup
Maniphest Tasks: T15901
Differential Revision: https://we.phorge.it/D25764