mkdirp method

Implementation

@override
Future<SafDocumentFile> mkdirp(String uri, List<String> names) async {
  final map = await methodChannel.invokeMapMethod<String, dynamic>('mkdirp', {
    'uri': uri,
    'names': names,
  });
  if (map == null) {
    throw Exception('Failed to create directory: $uri');
  }
  return SafDocumentFile.fromMap(map);
}