Make Edit>Undo available on macOS in the add cards screen

Due to https://github.com/ankitects/anki/pull/1486, users need to navigate to the main window before they can access Undo via the Edit menu. Perhaps we should add an Edit menu to the add cards screen as well, with undo/redo as an option.

Originally reported on https://forums.ankiweb.net/t/make-undo-button-and-or-ctrl-z-universally-available-especially-lacking-in-card-creation/47665

Start with the add cards screen and the current Edit menu behavior on macOS, using pull request 1486 for context. Done means users can access Edit > Undo and Redo from the add cards screen without navigating to the main window.

Written by the indexing model from the issue text.