app/internal/wm: use Option method to initialize windows

Added (*w.window).Option methods to the backends and use them for setting the initial options passed into NewWindow.

Signed-off-by: pierre <pierre.curto@gmail.com>

app/internal/wm/os_ios.go

@@ -239,6 +239,8 @@ func (w *window) WriteClipboard(s string) {
 	})
 }
 
+func (w *window) Option(opts *Options) {}
+
 func (w *window) SetAnimating(anim bool) {
 	v := w.view
 	if v == 0 {