Remove assumption of 1000x1000 size

[redblobgames]

Right now the library assumes the points will be 0 ≤ x ≤ 1000, 0 ≤ y ≤ 1000. What does this buy me? Is there any advantage to this limitation, or is just because that's the range I used for the map project this library came from?

[redblobgames]

V3 will take a bounds parameter {left: 0, top: 0, width: 1000, height: 1000} for the boundary point functions. The rest of the code will not assume a boundary.