EffectComposer: Add option for custom render pass

[shotamatsuda]

I've been trying MRT with EffectComposer in order to avoid additional render passes to output normals, masks, and so on. Extensibility is always a problem with pure components, but in this case, having a RenderPass prop in EffectComposer to accept a class implementing the same interface as RenderPass would allow us to use a custom render pass. Otherwise, and this is my current workaround, we must maintain a modified copy of EffectComposer, which is suboptimal in terms of maintainability.

Like:

export const EffectComposer = memo(
 forwardRef<EffectComposerImpl, EffectComposerProps>(
 (
 {
 ...,
 RenderPass = RenderPass
 },
 ref
 ) => {
 ...
 const [composer, normalPass, downSamplingPass] = useMemo(() => {
 ...
 // Add render pass
 effectComposer.addPass(new RenderPass(scene, camera))
 ...
 }, [
 ...,
 RenderPass
 ])
 ...
 }
 )
)

I'd like to hear your opinion.