RFC: support dbusmenu menu expanding

[Konstantin]

In cosmic-applets, you have https://github.com/pop-os/cosmic-applets/blob/master/cosmic-applet-status-area/src/components/status_menu.rs

And we can use it for standard menubars too. It can be regulated by something like "gtk-shell-shows-menubar" gsettings setting.

What do you think about it?

I do not know Rust, so, I just want to ask here.