feat(): spatial indexing

[ShaMan123]

Proposed Changes

Closes #26

Rebase onto #27

Introduces a spatial index interface that allows to query curve bbox and boost performance.

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[ShaMan123]

This PR shows that after #26 it is trivial to use the repo with a spatial index so I am OK with not having it part of the repo as long as we export the essentials.
But if we provide a built in index that would be valuable.