Dense Point Cloud capture

[danmonaghan]

Since ARKit 3.5 it's possible to capture from the LiDAR - given this is one of the few open source projects that actually captured a colour point cloud before this new feature, it seems like an update to ARVisualizer adding full depth input support would be fairly easy.
I've got all the code for point cloud capture from the LiDAR in SceneKit on hand and would be happy to contribute when I get a moment.

[tonyarnold]

Sounds great to me, @danmonaghan - feel free to file a PR when you have the time. Thanks!