Implement `delaunay!`, in-place version of `delaunay`

[fverdugo]

trafficstars

Now, delaunay allocates the output. It would be nice to have the corresponding in-place version delaunay!, where the user provides the output. A part of performance reasons, the in-place version would allow the user to select the container type (as long as it has the correct memory layout).

Once delaunay! is available, delaunay can be implemented by calling delaunay!.

[fverdugo]

Hi @kahaaga ! If you want to further contribute to the project. This would be a nice thing to have.