Function rotateY

rotateY(a, b, rad, dst?): Vec3
Rotate a 3D vector around the y-axis
Parameters
- a: Vec3
  The vec3 point to rotate
- b: Vec3
  The origin of the rotation
- rad: number
  The angle of rotation in radians
- Optional dst: Vec3
  The vector to set. If not passed a new one is created.
Returns Vec3
the rotated vector