function handleError(dracoLoader, error) {
  dracoLoader.unload();
  dracoLoader._state = ResourceLoaderState.FAILED;
  const errorMessage = "Failed to load Draco";
  throw dracoLoader.getError(errorMessage, error);
}
Loads the resource.
@returns {Promise<GltfDracoLoader>} A promise which resolves to the loader when the resource loading is completed.
@private