[linting_tool] Add Adaptive Layout with Theming (#852)

experimental/linting_tool/lib/app.dart

@@ -0,0 +1,40 @@
+// Copyright 2021 The Flutter team. 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:linting_tool/theme/app_theme.dart';
+import 'package:linting_tool/widgets/adaptive_nav.dart';
+import 'package:linting_tool/routes.dart' as routes;
+
+class LintingTool extends StatefulWidget {
+  const LintingTool({Key? key}) : super(key: key);
+
+  static const String homeRoute = routes.homeRoute;
+
+  @override
+  _LintingToolState createState() => _LintingToolState();
+}
+
+class _LintingToolState extends State<LintingTool> {
+  @override
+  Widget build(BuildContext context) {
+    return MaterialApp(
+      title: 'Flutter Linting Tool',
+      theme: AppTheme.buildReplyLightTheme(context),
+      darkTheme: AppTheme.buildReplyDarkTheme(context),
+      themeMode: ThemeMode.light,
+      initialRoute: LintingTool.homeRoute,
+      onGenerateRoute: (settings) {
+        switch (settings.name) {
+          case LintingTool.homeRoute:
+            return MaterialPageRoute<void>(
+              builder: (context) => const AdaptiveNav(),
+              settings: settings,
+            );
+        }
+        return null;
+      },
+    );
+  }
+}