networkSourceMatcher function 
 
    
    
    
  Implementation
  CustomRenderMatcher networkSourceMatcher({
  List<String> schemas = const ["https", "http"],
  List<String>? domains,
  String? extension,
}) =>
    (context) {
      if (context.tree.element?.attributes.cast() == null ||
          _src(context.tree.element!.attributes.cast()) == null) return false;
      try {
        final src = Uri.parse(_src(context.tree.element!.attributes.cast())!);
        return schemas.contains(src.scheme) &&
            (domains == null || domains.contains(src.host)) &&
            (extension == null || src.path.endsWith(".$extension"));
      } catch (e) {
        return false;
      }
    };