WebGLPathTracer: Possible improvements to investigate

[gkjohnson]

• https://dassaultsystemes-technology.github.io/EnterprisePBRShadingModel/spec-2022x.md.html#components/core/dielectricbsdffortransparentsurfaces
• https://twitter.com/lisyarus/status/1786523192229580945
• https://twitter.com/lisyarus/status/1786485914539028921