some things i need to do on nj export:
1. use separate buffer views and accessors for each mesh's vertex data (fixes importers duplicating all verts for each mesh)
2. different joint sets for each mesh even if verts are reused (should be basic MVP at this point)
3. parse UVs into the vertex data on a per-mesh basis
i really, really hope someone's got a tool to convert glTF2 to something _useful_