WebGPURenderer: Fix types for indirect compute and modify example to show usage

[TheBlek]

Related issue: #30982

Description

This is a follow-up PR for #31488

• Fix types for compute and computeAsync functions
• Handle indirect buffer in webgl backend gracefully
• In webgpu_compute_particles example make only half of the balls move based on an indirect buffer
• Respect dispatchSize when running computeAsync from compute on uninitialized renderer

cc: @sunag

[github-actions]

📦 Bundle size

Full ESM build, minified and gzipped.

	Before	After	Diff
WebGL	350.11 84.81	350.11 84.81	+0 B +0 B
WebGPU	605.24 169.71	605.42 169.77	+181 B +58 B
WebGPU Nodes	603.85 169.47	604.03 169.53	+181 B +53 B

🌳 Bundle size after tree-shaking

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

	Before	After	Diff
WebGL	481.77 119.56	481.77 119.56	+0 B +0 B
WebGPU	674.62 185.19	674.8 185.24	+182 B +54 B
WebGPU Nodes	616.61 168.41	616.79 168.47	+182 B +57 B

[sunag]

In webgpu_compute_particles example make only half of the balls move based on an indirect buffer

I think we'd better add this in another example.

[cmhhelgeson]

In webgpu_compute_particles example make only half of the balls move based on an indirect buffer

I think we'd better add this in another example.

Rain would probably be a better use case right? The number of compute droplets can be changed to equal the number of rendered droplets rather than always computing the maximum.