Mesh,Sprite: Add count property

[sunag]

Description

In WebGPURenderer instances are created through TSL functions, this allows for easier skinning and sprite instancing which is very useful for particles. Practically all webgpu examples of instances already use it, the property is just not declared.

[github-actions]

📦 Bundle size

Full ESM build, minified and gzipped.

	Before	After	Diff
WebGL	337.26 78.64	337.26 78.64	+0 B +0 B
WebGPU	548.43 152.04	548.43 152.04	+0 B +0 B
WebGPU Nodes	547.78 151.89	547.78 151.89	+0 B +0 B

🌳 Bundle size after tree-shaking

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

	Before	After	Diff
WebGL	467.33 112.95	467.34 112.95	+13 B +8 B
WebGPU	623.34 168.78	623.35 168.79	+13 B +7 B
WebGPU Nodes	578.19 158.07	578.2 158.07	+13 B +6 B

[Makio64]

@sunag while exploring the particles examples fews weeks ago i realize in webgpu renderer there are different approach of how make them in TSL, which approach will you recommend ?

[sunag]

There are two main approaches to particles. The deterministic one is useful for simple smoke, spark, fire effects for example. If you need particles that interact with the scene, objects, etc. I recommend compute particle.