[esc] doesn't work to close full-screen editor

[LogicalJoe]

Solutions include: adding a button to close the full-screen editor.

[LogicalJoe]

Update: [esc] does actually close the editor but only when the cursor is in the text input box. Could it be made to work when the textbox is not selected?

[Legend-of-iPhoenix]

I can repro this in chrome/firefox, this is not an issue specific to safari but rather one with the userstyle.
I'm certain that this is caused by the keyup event listener being on .posteditor_columns and not the window itself.

I think the merging of #38 resolves the underlying problem of the screen being annoying to close by adding a close button. I'll keep this issue open because it is unintuitive behavior worth looking at, though.