feat: Make the library usable from vanilla Three.js

[hmans]

It would be nice to make this library usable from vanilla React. A couple of notes/ideas/etc.:

• Currently, the only effect runner, <MeshParticles>, is implemented as a React component, assuming react-three-fiber. In feat: Composable Shaders #11, this component will probably undergo heavy refactoring. It would be a good opportunity to refactor the relevant code into a normal MeshParticles class that inherits from InstancedMesh. This class could then still be exposed to React via extend (or a normal component.)
• For materials, we're using three-custom-shader-material, which already lets you use its functionality imperatively, so there's probably nothing we need to do here.
• <Emitter> very conveniently is only a very thin wrapper around the spawnParticles function, which can also be called imperatively. There is probably no need to provide a vanilla equivalent to this React component.
• The library currently contains a lot of React niceties for declaratively creating animation waterfalls through the <Delay>, <Repeat> and <Lifetime> components. It should not be a goal to replicate these for imperative use. When using this library imperatively, users will most likely have their own animation primitives they can use.

[hmans]

This is now perfectly possible, thanks to VFX Composer :D