clone = (decoder, newPos = decoder.pos) => {
  const _decoder = createDecoder(decoder.arr);

  _decoder.pos = newPos;
  return _decoder;
}
Clone a decoder instance.
Optionally set a new position parameter.

@function
@param {Decoder} decoder The decoder instance
@param {number} [newPos] Defaults to current position
@return {Decoder} A clone of `decoder`