[Feature request] make an application move it windows

Hello,

I run into this issue (https://github.com/gotk3/gotk3/issues/397), I thought it was a bug or something and wanted to understand why its not working, so I asked on Gnome IRC and they said, that wayland doesn't let applications moves its windows.

It is possible to add this feature? I'm volunteer to work on it, but I din't touch C about 6 years... so maybe I'll need some help.

Regards, Younes