Spatial sorting for fast insertion

[DanielVandH]

It would be nice to have a method for sorting points in space, such as with a Hilbert sort. Obviously this could be provided by the user (with the point_order kwarg), but it would be nice to have a function in the code for ease of use. Will need to find some implementation for it that works for general points without any domain restrictions.

The main objective would be to implement a biased randomised insertion order (see Sec 5.3 of the Delaunay book) based on this spatial sorting.

[DanielVandH]

Reopening. Even if this is not something we put in the package directly, I want to have an example in the documentation showing how something like BijectiveHilbert.jl can do this. Some benchmarks would be nice.