cross method
Vector cross product @param target Optional target to save in.
Implementation
Vec3 cross(Vec3 vector, [Vec3? target]){
target ??= Vec3();
final vx = vector.x;
final vy = vector.y;
final vz = vector.z;
target.x = y * vz - z * vy;
target.y = z * vx - x * vz;
target.z = x * vy - y * vx;
return target;
}