Consider having an Application Window

Another polemic issue :)

RiseupVPN, in its current incarnation, is a systray-only app. But getting an icon showing in gnome is proving difficult - and we can suggest, but we probably cannot rely on extensions (like #303) to be installed.

So one option might be to bring back the "main" application window in certain situations (as a fallback, or also when clicking on some part of the menu).