Add documentation for experimental `local_to_ij` and `ij_to_local` about h3ron HOT 3 CLOSED

    #[test]
    fn test_local_ij() {
        let index = Index::try_from(0x89283080ddbffff_u64).unwrap();
        let ring = index.k_ring(1);
        assert_ne!(ring.len(), 0);
        let other = ring.iter().find(|i| **i != index).unwrap().clone();

        let coordij1 = h3_to_local_ij(&index, &index).unwrap();
        dbg!(coordij1.i);
        dbg!(coordij1.j);
        let coordij = h3_to_local_ij(&index, &other).unwrap();
        dbg!(coordij.i);
        dbg!(coordij.j);
        let other2 = local_ij_to_h3(&index, &coordij).unwrap();
        assert_eq!(other, other2);
    }

        let local_ijk = h3_to_local_ij(&index, &index).unwrap();
        let diff_ijk = h3_to_local_ij(&index, &neighbor_index).unwrap();
        let ijk = CoordIJ {
            i: diff_ijk.i - local_ijk.i,
            j: diff_ijk.j - local_ijk.j,
        };
        assert_eq!(ijk, CoordIJ { i: -1, j: -1 });

        let local_ijk = h3_to_local_ij(&neighbor_index, &neighbor_index).unwrap();
        let diff_ijk = h3_to_local_ij(&neighbor_index, &index).unwrap();
        let ijk = CoordIJ {
            i: diff_ijk.i - local_ijk.i,
            j: diff_ijk.j - local_ijk.j,
        };
        assert_eq!(ijk, CoordIJ { i: 1, j: 1 });