Implement glTF animation.

[ikeough]

Telling the story of how things go together in AEC is often done with animations that showing the assembly (or disassembly) of building systems.

Describe the solution you'd like
By implementing animations in glTF, and providing an API for users to create animations, we unlock the ability to do time-based story telling using Elements. This could be as simple as a door opening by animating a rotation transform, or an entire building system coming together by animating translation transforms. Because animation is natively supported in glTF viewers, the work required to integrate this into Hypar will require play controls and some hints about whether to auto-play animations.

Additional context
https://github.com/KhronosGroup/glTF-Tutorials/blob/master/gltfTutorial/gltfTutorial_007_Animations.md

[sanchez]

If we could have the ability to emit "steps" between functions this would be amazing, you could then show iterations of how the result was generated in the situation where you have a feedback loop generation within a function.

[sanchez]

Another option this might open is the ability for a user to have some basic filters to play through as well, in the instance of a building each step could be a level, so they can toggle between the levels and play with a specific level or the whole model?

[ikeough]

This work was begun in #869.