Fix warnings

@@ -260,7 +260,7 @@ void main() {
               text: '中文',
               style: TextStyle(font: asian),
             ),
-            TextSpan(
+            const TextSpan(
               text: ' world!',
             ),
           ],

 // ignore_for_file: always_specify_types
+// ignore_for_file: public_member_api_docs
 
 import 'package:flutter/material.dart';
 import 'package:pdf/widgets.dart' as pw;