Support for Distance Queries

[SallySoul]

This is sort of a feature request, but I would also be happy to work on implementing it!

I am experimenting with porting some of our C++ code to rust. I would love to use a community supported BVH implementation this time around. However, besides ray intersections, we also make extensive use of distance queries, i.e. what is the closest object/s in the BVH to arbitrary points.

Is this functionality y'all would be open to having in this crate?

I have some ideas on how that would look which I'd be happy to discuss, and there are some other queries I'd be willing to port over too like a Fast Winding Number, but I don't want to get ahead of myself or be overwhelming.

[svenstaro]

I think having this kind of feature would be excellent and I'd happily accept a PR.