Support undo/redo in code editor

[aabedraba]

While on cluster mode, I updated a file and then saved. Then I proceeded to take back my edits, but pressing cmd+z did not undo in the editor.

It would be really helpful to have this.

[olensmar]

@devcatalin I thought we had this - perhaps not in cluster-mode? or does the history get lost when saving?

[devcatalin]

I'll take a look, undo/redo should definitely work so maybe there's a bug