ScenegraphLayer: Support glTF KHR_materials_unlit extension

[ibgreen]

Target Use case

Photogrammetry is already lit, no additional lighting should be applied.

Proposed feature

• GLTFLoader in loaders.gl now supports this extension.
• Check material.unlit, in this case just render the base color texture.

To Do List

• Add label and assign to milestone
• Coding
• Doc update
• What’s new update
• Test

[ibgreen]

AFAIK, this is only handled in loaders.gl. It also needs to be handled in luma.gl lighting modules and verified/plumbed through in deck.gl.

Use case: This extension is needed for supporting 3d tiles with photogrammetry.

Maybe move this to v8.x instead of closing?

[tgorkin]

Sorry, incorrectly assumed this was complete as part of the linked PR.