Make UserInputService.JumpRequest() fire when the mobile jump button is pressed

There’s no good way to detect jump button presses on mobile devices, and you’d expect JumpRequest to have this as an included behavior. Instead, it currently only works on PCs.

I can’t use Humanoid.StateChanged() or Humanoid.Jumping() because I need to detect when a jump is requested (for the double-jump perk in Super Bomb Survival), not when the player actually jumps.