Issue with multiple joysticks

[Xamyrz]

Describe the bug
the "touchend" event should be listening to "canvas" rather than "document", as in my webapp, when i want to have 2 joysticks, and I let go of one of them, the "touchend" event gets fired on both of the joysticks.

To Reproduce
Steps to reproduce the behavior:

1. add 2 joysticks
2. touch 2 at the same time
3. let go of one
4. "touchend" will be fired for both joysticks, rather than just the one.

Expected behavior
touchend fired on the joystick that actually initialised it, rather than both

Screenshots

Desktop (please complete the following information):

• OS: [e.g. iOS]
• Browser [e.g. chrome, safari]
• Version [e.g. 22]

Smartphone (please complete the following information):

• Device: [e.g. iPhone6] ALL DEVICES
• OS: [e.g. iOS8.1] ALL OS's
• Browser [e.g. stock browser, safari] ALL BROWSERS
• Version [e.g. 22] ALL

Additional context
None