Adding JSON example. (#1)

jsonexample/lib/main.dart

@@ -0,0 +1,69 @@
+// Copyright 2018 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+import 'package:flutter/material.dart';
+import 'package:jsonexample/tab_pages.dart';
+
+void main() => runApp(MyApp());
+
+class MyApp extends StatelessWidget {
+  @override
+  Widget build(BuildContext context) {
+    return MaterialApp(
+      title: 'Flutter Demo',
+      theme: ThemeData(
+        primarySwatch: Colors.blue,
+      ),
+      home: MyHomePage(),
+    );
+  }
+}
+
+class MyHomePage extends StatelessWidget {
+  MyHomePage({Key key}) : super(key: key);
+
+  @override
+  Widget build(BuildContext context) {
+    return DefaultTabController(
+      length: 10,
+      child: Scaffold(
+        appBar: AppBar(
+          title: const Text('Let\'s parse some JSON'),
+          bottom: const TabBar(
+            isScrollable: true,
+            tabs: [
+              Tab(text: 'Basics'),
+              Tab(text: 'Conv. Simple'),
+              Tab(text: 'Conv. Complex'),
+              Tab(text: 'Conv. List'),
+              Tab(text: 'Ser. Simple'),
+              Tab(text: 'Ser. Complex'),
+              Tab(text: 'Ser. List'),
+              Tab(text: 'Built Simple'),
+              Tab(text: 'Built Complex'),
+              Tab(text: 'Built List'),
+            ],
+          ),
+        ),
+        body: new SafeArea(
+          bottom: false,
+          child: TabBarView(
+            children: [
+              BasicsPage(),
+              ConvertedSimplePage(),
+              ConvertedComplexPage(),
+              ConvertedListPage(),
+              SerializableSimplePage(),
+              SerializableComplexPage(),
+              SerializableListPage(),
+              BuiltSimplePage(),
+              BuiltComplexPage(),
+              BuiltListPage(),
+            ],
+          ),
+        ),
+      ),
+    );
+  }
+}