decodeHex function
Decodes hex value and converts to Buffer of Uint8List
Implementation
Uint8List decodeHex(String value) {
  if (value.startsWith('0x')) {
    value = value.substring(2);
  }
  try {
    return Uint8List.fromList(hex.decode(value));
  } catch (_) {
    throw HexException(value);
  }
}