Add game_template (#1180)

Adds a template / sample for games built in Flutter, with all the bells and whistles, like ads, in-app purchases, audio, main menu, settings, and so on.

Co-authored-by: Parker Lougheed
Co-authored-by: Shams Zakhour

game_template/lib/src/win_game/win_game_screen.dart

@@ -0,0 +1,73 @@
+// Copyright 2022, the Flutter project authors. Please see the AUTHORS file
+// for details. 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:go_router/go_router.dart';
+import 'package:provider/provider.dart';
+
+import '../ads/ads_controller.dart';
+import '../ads/banner_ad_widget.dart';
+import '../games_services/score.dart';
+import '../in_app_purchase/in_app_purchase.dart';
+import '../style/palette.dart';
+import '../style/responsive_screen.dart';
+
+class WinGameScreen extends StatelessWidget {
+  final Score score;
+
+  const WinGameScreen({
+    Key? key,
+    required this.score,
+  }) : super(key: key);
+
+  @override
+  Widget build(BuildContext context) {
+    final adsControllerAvailable = context.watch<AdsController?>() != null;
+    final adsRemoved =
+        context.watch<InAppPurchaseController?>()?.adRemoval.active ?? false;
+    final palette = context.watch<Palette>();
+
+    const gap = SizedBox(height: 10);
+
+    return Scaffold(
+      backgroundColor: palette.backgroundPlaySession,
+      body: ResponsiveScreen(
+        squarishMainArea: Column(
+          mainAxisAlignment: MainAxisAlignment.center,
+          children: <Widget>[
+            if (adsControllerAvailable && !adsRemoved) ...[
+              const Expanded(
+                child: Center(
+                  child: BannerAdWidget(),
+                ),
+              ),
+            ],
+            gap,
+            const Center(
+              child: Text(
+                'You won!',
+                style: TextStyle(fontFamily: 'Permanent Marker', fontSize: 50),
+              ),
+            ),
+            gap,
+            Center(
+              child: Text(
+                'Score: ${score.score}\n'
+                'Time: ${score.formattedTime}',
+                style: const TextStyle(
+                    fontFamily: 'Permanent Marker', fontSize: 20),
+              ),
+            ),
+          ],
+        ),
+        rectangularMenuArea: ElevatedButton(
+          onPressed: () {
+            GoRouter.of(context).pop();
+          },
+          child: const Text('Continue'),
+        ),
+      ),
+    );
+  }
+}