addService method
Adds a service with |serviceUuid| to the peripheral with |address|. Returns: An identifier that uniquely represents this service.
Implementation
Future<String> addService(String address, String serviceUuid) async {
  var result = await _client.send('BluetoothEmulation.addService', {
    'address': address,
    'serviceUuid': serviceUuid,
  });
  return result['serviceId'] as String;
}