app: add support for system cursors

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

app/internal/window/os_ios.go

@@ -51,6 +51,7 @@ type window struct {
 
 	layer   C.CFTypeRef
 	visible atomic.Value
+	cursor  pointer.CursorName
 
 	pointerMap []C.CFTypeRef
 }
@@ -249,6 +250,10 @@ func (w *window) SetAnimating(anim bool) {
 	}
 }
 
+func (w *window) SetCursor(name pointer.CursorName) {
+	w.cursor = windowSetCursor(w.cursor, name)
+}
+
 func (w *window) onKeyCommand(name string) {
 	w.w.Event(key.Event{
 		Name: name,