startcustomprinting method

Implementation

@override
Future<TransactionMonitor> startcustomprinting(List<Widget> template) async {
  Map<String, String> args = {
    "textprint": printmodelToJson(await printcomponent(template)),
  };
  var result = await methodChannel.invokeMethod("startcustomprint", args);
  return transactionMonitorFromJson(jsonEncode(result));
}