Add 'material' command to CLI to add/modify textures and properties

Proposed usage:

gltf-transform material input.glb output.glb \
  --baseColorTexture base-color.png \
  --transmissionTexture transmission.png \
  --ior 1.5

This should automatically add the appropriate extensions.

[dbuck]

No, I misread my results, realized right after that that it won’t allow external references in the written glb

[dbuck]

Just wanted to tag on here that I also found that hint helpful, I was looking to use the package to work with some gltf files, but needed to have external textures at the final step, this worked to export out the embedded textures, but wasn’t clear from the docs.

for (const tex of gltfDocument.getRoot().listTextures()) {
   tex.setURI(tex.getName() + '.jpg');
};