This reverts commit 8053b6f9.

* convert to ES modules

* rebuild

* move shaders back into glsl files

* reinstate polyfills

* start of background pass test.

* get clear pass and texture pass working well with each other.

* cube texture pass works.  render pass now obeys Pass.clear.  CubeTexturePass supports opacity.  TexturePass doesn't write to the depth buffer.

* get rid of temp matrix.

* add to files.js.  better title.

* remove unused scene parameter from CubeTexturePass.

* clear coat implementation.

* add physical variations to examples.

* add example file for physical materials

* adjust clearcoat range to 0-1 as original.

* switch example color to gray from yellow.

* add ability to specify on MeshDepthMaterial the type of depth packing one wants.

* depthRGBA -> clipZRGBA - more correct name.

* forgotten replace of depthRGBA -> clipZRGBA.

* add MeshDepthMaterial depthFormat + depthPacking.  Use equations compatible with z buffers.

* adopting MeshDepthMaterial instead of clipZRGBA.

* remove clipZRGBA shader (aka depthRGBA shader) as we can now use MeshDepthMaterial for it.

* remove some comments.

* enable skinning in MeshDepthMaterial, as it was enabled in depthRGBA material.

* remove unused shader.

* fix bug.

* fix bug in shadows with MEshDepthMaterial.

* remove unnecessary debug code.

* ensure that skinning and morphTargets propagate with MeshDepthMaterial.

* fix ssao example to use new MeshDepthMaterial.

* remove unused code.

* Reintroduce MeshPhysicalMaterial

* Reintroduce MeshPhysicalMaterial

* Simplified conditionals

add ability to have texel encodings (RGBE,RGBM,etc.) on envMap and emissiveMap that can contain unbounded intensities.

Refactored shadowmap code again. Android/Adreno doesn't fails to support bool and mat4 in structs...