message: gltfpack: Switch to KHR_quantized_geometry
  Now that KHR_quantized_geometry is an official KHR extension draft, this
  change switches to producing files with that extension instead of
  MESHOPT_ prefixed one.
  Additionally we mark the KHR_ extension as required. This fixes
  validation error highlighting the fact that this extension can't be
  optional.
diff: @@ -3443,8 +3443,9 @@ void process(cgltf_data* data, std::vector<Mesh>& meshes, const Settings& settin
  json.append(data->json + data->asset.extras.start_offset, data->json + data->asset.extras.end_offset);
  }
  append(json, "}");
  +
  append(json, ",\"extensionsUsed\":[");
  - append(json, "\"MESHOPT_quantized_geometry\"");
  + append(json, "\"KHR_quantized_geometry\"");
  if (settings.compress)
  {
  comma(json);
  @@ -3471,16 +3472,15 @@ void process(cgltf_data* data, std::vector<Mesh>& meshes, const Settings& settin
  append(json, "\"KHR_lights_punctual\"");
  }
  append(json, "]");
  +
  + append(json, ",\"extensionsRequired\":[");
  + append(json, "\"KHR_quantized_geometry\"");
  if (settings.compress && !settings.fallback)
  {
  - append(json, ",\"extensionsRequired\":[");
  - // Note: ideally we should include MESHOPT_quantized_geometry in the required extension list (regardless of compression)
  - // This extension *only* allows the use of quantized attributes for positions/normals/etc. This happens to be supported
  - // by popular JS frameworks, however, Babylon.JS refuses to load files with unsupported required extensions.
  - // For now we don't include it in the list, which will be fixed at some point once this extension becomes official.
  + comma(json);
  append(json, "\"MESHOPT_compression\"");
  - append(json, "]");
  }
  + append(json, "]");
  if (!views.empty())
  {
  