Hilbert R-Trees

Implement the [Hilbert R-Tree](https://en.wikipedia.org/wiki/Hilbert_R-tree) Data Structure.

The issue only names the data structure and a Wikipedia link. Start by reading the repository's existing tree implementations to understand the codebase structure. Then research Hilbert R-Trees to design the class interface and algorithms. 'Done' means a complete, tested implementation integrated into the library.

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