fix: allow pipeline options in post-processing sub passes

[dmnsgn]

Currently we're only able to pass blend.

pex-renderer/systems/render-pipeline/post-processing.js

Line 95 in 3b21fe1

{ blend: subPass.blend },

That would allow changing blending parameters e.g. premultiply alpha pipeline.

[vorg]

There is also need for clearColor: [0,0,0,0] and at this stage is this robust solution? Or should we wait for better renderPipeline where fully custom passes can be injected?

[dmnsgn]

clearColor is already available:

pex-renderer/systems/render-pipeline/post-processing/ssao.js

Lines 111 to 113 in 3b21fe1

	passDesc: () => ({
	clearColor: [0, 0, 0, 1],
	}),

It is only pipeline options that are missing.

Or should we wait for better renderPipeline where fully custom passes can be injected?

Although not super user-friendly, it is already possible to push effects to renderPipelineSystem.postProcessingEffects.