Adjustment to allow support for modern gamepads.

Created by: ishax-kos

Sony's PlayStation 4 controller has one more button than there were keywords usable in Godot controller mappings. This probably applies to Nintendo controllers, though I don't have a pro controller to test that theory with. I find it strange this was not in already. We can discuss the naming of it. I chose "touchpad" since that's what it is on Sony controllers. It could just as easily be "share" to match Nintendo. Of course "share" is also on Sony controllers but it equates to select, back and minus on different controllers.