function max(out, a, b) {
    out[0] = Math.max(a[0], b[0]);
    out[1] = Math.max(a[1], b[1]);
    return out;
  }
Returns the maximum of two vec2's

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