Add Shortcuts Window demo

[sonnyp]

https://docs.gtk.org/gtk4/class.ShortcutsWindow.html

[sonnyp]

All demos should be available in JS
So that's a good starting point.

Look at other similar demos are done such as Preferences Window

[sonnyp]

You can start in Python, but the demo won't be accepted unless it has a JavaScript version

[imhemish]

All demos should be available in JS So that's a good starting point.

Look at other similar demos are done such as Preferences Window

I don't get why this needs to be in JS, there is no dynamic functionality in Shortcuts Window. In my opinion, it should just be a pure blueprint implementation.

[sonnyp]

Because the demo needs a button to open the ShortcutsWindow

[sonnyp]

"Preferences Dialog" can be used as inspiration