UI QOL: Enable more media keys in tag editor

[GiovanH]

Currently the tag editor will let you manipulate the separate media viewer window in a few ways, such as the page down and page up keys. Additional keys (namely the F7 archive toggle) should work from this window, or the keyboard shortcut system should be extended to allow it.

The keyboard shortcut ALMOST seems to handle it currently:

Except these advanced commands are not user-accessible, and it's not possible to extend the system manually.

This issue could be obviated entirely by #1337, where the tag/media windows can be the same.

[GiovanH]

This is especially bad because for some reason the tag viewer doesn't show up as a window in Alt+tab, so a mouse movement is required to tag and approve images.