:wrench: Keep the slide processing when running directly

Easier to test ; the processing management is designed to work in a
slideshow only.

Actually, having a slide as the direct child of Window is like having
the focus.

godot/addons/slide_show/projector/slide/Slide.gd

@@ -23,7 +23,7 @@ func _ready() -> void:
 func disable() -> void:
 	set_process_unhandled_key_input(false)
 
-	if processing_keep_when_disabled:
+	if processing_keep_when_disabled or get_parent() is Window:
 		return
 	get_children().all(disable_processing)