reference:
- https://threejs.org/docs/index.html#examples/en/loaders/MTLLoader

example:
- https://unpkg.com/three@0.160.0/build/three.module.js
- https://unpkg.com/three@0.160.0/examples/jsm/controls/OrbitControls.js
- https://unpkg.com/three@0.160.0/examples/jsm/loaders/GLTFLoader.js

*note*: update the file to get the right import location
