Build up threejs scenes from R

[bwlewis]

We've added a new basic render function that simply displays threejs scenes, optionally with animation. For example:

library(threejs)
render(gzfile(system.file("extdata/pump.json.gz", package="threejs")), bg="black")

The plan is to add a relatively small set of R functions that mirror a subset of the native threejs functions to build up scenes. Example functions could include adding textures, meshes, geometries, etc. See https://threejs.org/docs/index.html#manual/introduction/Creating-a-scene for details.

Ideas and contributions welcome!