bindings for LibAdwaita

[WebFreak001]

with GTK 4 libadwaita was/is getting introduced, it contains a lot of responsive widgets.

[KonstantIMP]

It works on linux and need compile binaries for windows: https://github.com/KonstantIMP/d_adw
And it need more examples

[WebFreak001]

@MikeWey LibAdwaita 1.0 is now properly released, maybe it can be integrated into GtkD now? (See KonstantIMP/d_adw#4 for example gir-to-d files)

Would fit well for when you merge the gtk4 branch into master in the future too

[MikeWey]

It does fit nicely with Gtk4, i'll take a closer look when i have more time.