Godot glTF KHR_xmp_json_ld Copyright

Godot implementation of the glTF KHR_xmp_json_ld extension for DCMI copyright metadata. Requires Godot 4.3 or newer with this PR.

The addon is licensed under The Unlicense. Anyone is free to use this without restriction. Credit is appreciated but not required.

The test model is licensed under CC-BY-4.0, created by Mr. Snark (https://sketchfab.com/Mr-Snark). The full copyright details are in the .gltf file (remember, the whole point of this repo is an addon for storing copyright metadata in glTF files).

When exporting a glTF file from Godot, you should see this menu: