If provided, the callback will be passed to each resource URL before a request is sent. The callback may return the original URL, or a new URL to override loading behavior. This behavior can be used to load assets from .ZIP files, drag-and-drop APIs, and Data URIs.
Optional
callback: (url: string) => stringURL modifier callback. Called with url argument, and must return resolved URL.
The Mesh API encapsulates object that concerns mesh loading.