Expose bevy::pbr::gltf module.

[eswartz]

Objective

This allows users to reuse standard_material_from_gltf_material given the 0.19 changes to expose GltfMaterial instead of StandardMaterial.

Clients that iterate Gltf and GltfMesh to reclaim the ability to manually instantiate the materials from GltfMaterial as in 0.18.

See https://discord.com/channels/691052431525675048/749332104487108618/1521606712623235082

Solution

• Expose bevy::pbr::gltf as pub. It only exposes the given function as pub.

(An alternative is to provide pub use standard_material_from_gltf_material from bevy::pbr, but that makes the client use bevy::pbr::standard_material_from_gltf_material which might be confusing.

Testing

• Tested with my code that can now use use bevy::pbr::gltf::standard_material_from_gltf_material;.

[ChristopherBiscardi]

You don't need this to access the StandardMaterials being loaded, but it is nonetheless useful to make it public.