Order independent transparency example

[mikolalysenko]

Would be nice to have an order independent transparency demo for regl. Some starting points:

• Weighted order independent transparency
• https://cesiumjs.org/2014/03/14/Weighted-Blended-Order-Independent-Transparency/
• http://www.floored.com/blog/2015webgl-order-independent-transparency-single-render-target/

[guybrush]

@arose implemented this with threejs: mrdoob/three.js#4814

the demo-link in the issue is broken, i copy-pasted it into a htmleditor: http://tinyurl.com/ht7xp4p

[Erkaman]

We could possibly use that demo as our foundation. But our demo should be more complex, I think. It should be drawing 3D objects with transparency instead of just some silly quads. That would be cool I think.

Anyways, anyone who feels like porting that demo over to regl is very much welcome to give it a stab!