def append_data(data)
      data = Encoding::ASCII_8BIT == data.encoding ? data : data.htb
      chunks << Bitcoin::Script.pack_pushdata(data)
      self
    end
def append_data(data)
      data = Encoding::ASCII_8BIT == data.encoding ? data : data.htb
      chunks << Bitcoin::Script.pack_pushdata(data)
      self
    end
append data to payload with pushdata opcode
 @param [String] data append data. this data is not binary
 @return [Script] return self