Function rotate

rotate(m, angleInRadians, dst?): Mat3
Rotates the given 3-by-3 matrix by the given angle.
Parameters
- m: Mat3
  The matrix.
- angleInRadians: number
  The angle by which to rotate (in radians).
- Optional dst: Mat3
  matrix to hold result. If not passed a new one is created.
Returns Mat3
The rotated matrix.