Function normalise 

pub fn normalise<T>(a: &Vector3<T>, min_sq_value: T) -> Option<Vector3<T>>
where
    T: Float + Scalar + ComplexField<RealField = T>,

Normalize a vector to lie on the surface of the unit sphere.

Note: this function returns an Option so uses the British spelling of normalise to differentiate it from the standard normalize function.

• a the Vector3
• min_sq_value the minimum square of a vector length to normalize.

return the nomalized point or None if the vector is too small to normalize.