Codesplit WebGL/WebGPU entrypoints: Fix WebGPU Addons

[RenaudRohlinger]

Related PR: #29404

Description
Following #29404, fixes webgpu addons resolution with bundlers.
Related comment: #29404 (comment)

Which makes me think that we could even do better by establishing best practices across all WebGPU examples by standardizing proper imports:

<script type="importmap">
	{
		"imports": {
			"three": "../build/three.core.js",
			"three/webgpu": "../build/three.webgpu.js",
			"three/tsl": "../build/three.webgpu.nodes.js",
			"three/addons/": "./jsm/"
		}
	}
</script>

<script type="module">

	import * as THREE from 'three';
	import { WebGPURenderer } from 'three/webgpu'
	import { color, ... } from 'three/tsl';

This contribution is funded by Utsubo