Fix Suggenstion for HDRP

Version 2.10.0-rc displays pink materials with HDRP and Unity 2022.3.12. Below is a suggested fix, and I hope you will find helpful.

In line 3 of PBRHelpers.cginc:
https://github.com/KhronosGroup/UnityGLTF/blob/20b7493dbd6039fe2fd88e7c5a564ab3bd72734d/Runtime/Shaders/ShaderGraph/PBRHelpers.cginc#L3

SHADERGRAPH_PREVIEW must be replaced by another ShaderKeyword used in HDRP, such as SHADERPASS_FORWARD, because it has been removed in the current version of HDRP. Note that SHADERPASS_FORWARD is just an example.
Reference: https://issuetracker.unity3d.com/issues/shadergraph-number-if-shadergraph-preview-in-a-custom-function-node-throws-error

The two functions, SampleSceneColor_float and SampleSceneColor_half, from lines 52 to 72 in PBRHelpers.cginc:
https://github.com/KhronosGroup/UnityGLTF/blob/20b7493dbd6039fe2fd88e7c5a564ab3bd72734d/Runtime/Shaders/ShaderGraph/PBRHelpers.cginc#L52-L72
should be nested out of the conditional #if defined(USE_CAMERA_OPAQUE), as this conditional is not executed when HDRP is enabled.

Additionally, for improved convenience, within the Graph Inspector of PBRGraph.shadergraph, HDRP's Surface Type should be Opaque instead of Transparent and Alpha Clipping should be enabled as it is frequently used in many materials.

Start with Runtime/Shaders/ShaderGraph/PBRHelpers.cginc, especially the preview conditional and the SampleSceneColor functions described in the issue. Then inspect PBRGraph.shadergraph in Unity 2022.3.12 with HDRP and verify the relevant shader keywords and Graph Inspector settings. Done means HDRP materials no longer render pink, the shader compiles, and the graph uses the requested surface and clipping defaults.