Cottontail TODOs

• Make texture upload use of ImageBitmaps when available
• Generally reduce use of GL enums at user level
• Clean up Scene logic, maybe rename to WebXRSampleScene?
• Node cloning has issues, doesn't handle renderer changes.

Nice to haves

• Support GLTF skeletal animations
• Support Draco compression
• "Floaties"
• HTML-to-texture for captions. (SVG?)