docs: public static byte[] concat(Bytes b1, Bytes b2) {
      int offset = 0;
      int size = b1.length() + checkVlen(b1.length()) + b2.length() + checkVlen(b2.length());
  
      byte[] data = new byte[size];
  
      offset = writeVint(data, offset, b1.length());
      b1.copyTo(data, offset);
      offset += b1.length();
  
      offset = writeVint(data, offset, b2.length());
      b2.copyTo(data, offset);
  
      return data;
    }