Use shader material written in wgsl as shadow depth wrapper

[shen-lin]

Allow ShaderMaterial written in WGSL to be used as shadow depth wrapper.

Original issue discussion

Changes involved

• Avoids GLSL specific shader includes to be called when using WGSL for shadow depth wrapper.
• This PR does not implement shadow map specific shader includes in WGSL. When option doNotInjectCode=false, BJS will log error in dev tool console about missing shader includes by default. The reason is BJS does not yet have full support for StandardMaterial or PBRMaterial implemented in WGSL. It is a lot of work to setup WGSL shader from scratch with transparent shadows, self shadow, etc to test the missing shader includes for shadow map. The idea is: for now, if a developer has implement a complete WGSL shader that require these shader includes, this developer can create these shader includes in WGSL, and include them in ShaderStore.IncludesShadersStoreWGSL. This example has been tested with some dumm WGSL code included into final runtime WGSL shader. If I later on need these shader includes and I have a test case, I will implement them and add to BJS WGSL shader include.

The shader includes that could be added in the future (WGSL version) mentioned above refers to:

• shadowMapVertexExtraDeclaration
• shadowMapVertexNormalBias
• shadowMapVertexMetric
• shadowMapFragmentSoftTransparentShadow
• shadowMapFragment

Example outcome

See dev branch for test scenario setup in dev host.

Screenshot of local test result as shown below. A WGSL vertex shader is applied to animate both sphere and shadow vertex displacement.

[bjsplat]

Please make sure to label your PR with "bug", "new feature" or "breaking change" label(s).
To prevent this PR from going to the changelog marked it with the "skip changelog" label.

[bjsplat]

Please make sure to label your PR with "bug", "new feature" or "breaking change" label(s).
To prevent this PR from going to the changelog marked it with the "skip changelog" label.

[bjsplat]

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[Popov72]

Only a small change!

[Popov72]

Just missing a doc and we are ready to merge!