Add flutter_web samples (#75)

web/dad_jokes/lib/main.dart

@@ -0,0 +1,17 @@
+import 'package:flutter_web/material.dart';
+import 'main_page.dart';
+
+void main() => runApp(MyApp());
+
+class MyApp extends StatelessWidget {
+  @override
+  Widget build(BuildContext context) {
+    return MaterialApp(
+      title: 'Dad Jokes',
+      theme: ThemeData(
+        primarySwatch: Colors.deepOrange,
+      ),
+      home: MainPage(title: 'Dad Jokes'),
+    );
+  }
+}