Adds the start of a new sample showcasing Cupertino widgets. (#12)

veggieseasons/lib/screens/list.dart

@@ -0,0 +1,22 @@
+// Copyright 2018 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/cupertino.dart';
+import 'package:flutter/widgets.dart';
+import 'package:veggieseasons/styles.dart';
+
+class ListScreen extends StatelessWidget {
+  @override
+  Widget build(BuildContext context) {
+    return CupertinoPageScaffold(
+      navigationBar: CupertinoNavigationBar(
+        middle: Text('List'),
+      ),
+      backgroundColor: Styles.scaffoldBackground,
+      child: Center(
+        child: Text('Not yet implemented.'),
+      ),
+    );
+  }
+}