docs: public static String toBase58WithChecksum(byte[] b) {
          byte[] cs = Hash.hash(b);
          byte[] extended = new byte[b.length + 4];
          System.arraycopy(b, 0, extended, 0, b.length);
          System.arraycopy(cs, 0, extended, b.length, 4);
          return toBase58(extended);
      }