Support glTF/glb PBR Next (glTF 2.0 Extensions) included in IridescentDishWithOlives

[coderextreme]

(no rush, I can view it with three.js and babylon.js fairly well.

https://github.com/KhronosGroup/glTF-Sample-Models/tree/master/2.0/IridescentDishWithOlives

(looking for an integration with X3D).

Thanks!