Function robust::insphere

pub fn insphere<T: Into<f64>>(
    pa: Coord3D<T>,
    pb: Coord3D<T>,
    pc: Coord3D<T>,
    pd: Coord3D<T>,
    pe: Coord3D<T>
) -> f64

Returns a positive value if the point pe lies inside the sphere passing through pa, pb, pc, and pd.
Returns a negative value if it lies outside.
Returns 0 if the five points are cospherical.
NOTE: The points pa, pb, pc, and pd must be ordered so that they have a positive orientation.