[EventSystem] tap event never fires

[SerG-Y]

Tap event never fires on mobile or even in Chrome device simulator.

The root cause of this issue is in normalizeToPointerData function

pixijs/packages/events/src/EventSystem.ts

Lines 499 to 500 in f215d87

	if (typeof touch.button === 'undefined') touch.button = event.touches.length ? 1 : 0;
	if (typeof touch.buttons === 'undefined') touch.buttons = event.touches.length ? 1 : 0;

So, on touchstart event event.touches.length equal to 1 but when your remove finger and on touchend event it equal to 0. It means that we map it to different buttons in trackingData.clicksByButton which cause the issue. Regarding to the spec (https://w3c.github.io/pointerevents/#the-button-property) we should always use 0 for button and 1 for buttons.

Expected Behavior

tap event fires

Current Behavior

tap event never fires

Possible Solution

The solution would be easy like

if (typeof touch.button === 'undefined') touch.button = 0; 
if (typeof touch.buttons === 'undefined') touch.buttons = 1; 

Steps to Reproduce

Before visiting pixiplayground make sure that the mobile emulator is enabled (important)
https://www.pixiplayground.com/#/edit/M7QmJOCtsKqeUo1JJq-T5

Environment

Doesn't matter in this case