function multiply(out, a, b) {
    out[0] = a[0] * b[0];
    out[1] = a[1] * b[1];
    return out;
  }
Multiplies two vec2's

@param {vec2} out the receiving vector
@param {ReadonlyVec2} a the first operand
@param {ReadonlyVec2} b the second operand
@returns {vec2} out