Adding shrine. (#3)

Adds a new version of Shrine from the MDC codelabs.

shrine/lib/colors.dart

@@ -0,0 +1,28 @@
+// Copyright 2018-present the Flutter authors. All Rights Reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+import 'package:flutter/material.dart';
+
+const kShrinePink50 = const Color(0xFFFEEAE6);
+const kShrinePink100 = const Color(0xFFFEDBD0);
+const kShrinePink300 = const Color(0xFFFBB8AC);
+const kShrinePink400 = const Color(0xFFEAA4A4);
+
+const kShrineBrown900 = const Color(0xFF442B2D);
+const kShrineBrown600 = const Color(0xFF7D4F52);
+
+const kShrineErrorRed = const Color(0xFFC5032B);
+
+const kShrineSurfaceWhite = const Color(0xFFFFFBFA);
+const kShrineBackgroundWhite = Colors.white;