WebXRController: Add grip update event if enabled.

[danrossi]

Related issue: #32353 #33118

Description

Adds a grip update event to the WebXRController to individually handle gamepad and input source for each controller. The event can be enabled / disabled easily so it's not being called all the time.

I found trying to handle gamepad inputs externally for each controller connected is clunky and should be handled in an event. I was forced to make a patched XRController to do this.

A gamepad helper can then use this event to handle gamepad inputs and dispatch specific events like in my patched XRController. Perhaps this can be added to the examples also.

https://github.com/danrossi/three-xr-controller/blob/main/src/XRController.js#L79

[github-actions]

📦 Bundle size

Full ESM build, minified and gzipped.

	Before	After	Diff
WebGL	359.27 85.31	359.27 85.31	+0 B +0 B
WebGPU	630.13 174.94	630.13 174.94	+0 B +0 B
WebGPU Nodes	628.72 174.69	628.72 174.69	+0 B +0 B

🌳 Bundle size after tree-shaking

Minimal build including a renderer, camera, empty scene, and dependencies.

	Before	After	Diff
WebGL	491.03 119.72	491.13 119.74	+102 B +26 B
WebGPU	703.7 189.99	703.8 190.02	+102 B +27 B
WebGPU Nodes	652.93 177.41	653.03 177.44	+102 B +26 B

[danrossi]

It's done

[danrossi]

Thanks for the refactored change. I have updated my gamepad feature on my side. https://github.com/danrossi/three-xr-controller-manager/blob/master/src/webxr/XRGamepad.js#L80