function scale(out, a, v) {
  let x = v[0],
    y = v[1];

  out[0] = x * a[0];
  out[1] = x * a[1];
  out[2] = x * a[2];

  out[3] = y * a[3];
  out[4] = y * a[4];
  out[5] = y * a[5];

  out[6] = a[6];
  out[7] = a[7];
  out[8] = a[8];
  return out;
}
Scales the mat3 by the dimensions in the given vec2

@param {mat3} out the receiving matrix
@param {ReadonlyMat3} a the matrix to scale
@param {ReadonlyVec2} v the vec2 to scale the matrix by
@returns {mat3} out