Update window demo for libadwaita 1.5

[sonnyp]

See the first example here https://gnome.pages.gitlab.gnome.org/libadwaita/doc/main/class.Window.html

[sonnyp]

This requires GNOME 46 so you will need to use Workbench development from main

https://github.com/workbenchdev/Workbench

[Sahil-Shadwal]

By workbench env you mean, we have to access the window demo from workbench sub-module, right?

[sonnyp]

You have to run Workbench from git (GNOME Builder is easiest)

https://github.com/workbenchdev/Workbench

Then from Workbench Devel open the demos from the demos repository.

[Sahil-Shadwal]

Will make PR soon.

[Siddhi0135]

@sonnyp is this issue still open? if yes , i would love to give it a try

[sonnyp]

I took care of it in #71