Re-add Craig Labenz's code sharing sample (#1466)

* Revert "Revert "Add code sharing sample (#1444)" (#1464)"

This reverts commit dc50c46ef1.

* Opting out failing tests on Windows for CI

Co-authored-by: Craig Labenz <craig.labenz@gmail.com>

code_sharing/server/bin/server.dart

@@ -0,0 +1,36 @@
+import 'dart:convert';
+import 'dart:io';
+
+import 'package:shared/shared.dart';
+import 'package:shelf/shelf.dart';
+import 'package:shelf/shelf_io.dart';
+import 'package:shelf_router/shelf_router.dart';
+
+int count = 0;
+
+// Configure routes.
+final _router = Router()
+  ..post('/', _incrementHandler)
+  ..get('/', _getValueHandler);
+
+Future<Response> _incrementHandler(Request request) async {
+  final incr = Increment.fromJson(json.decode(await request.readAsString()));
+  count += incr.by;
+  return Response.ok(json.encode(Count(count).toJson()));
+}
+
+Response _getValueHandler(Request request) =>
+    Response.ok(json.encode(Count(count).toJson()));
+
+void main(List<String> args) async {
+  // Use any available host or container IP (usually `0.0.0.0`).
+  final ip = InternetAddress.anyIPv4;
+
+  // Configure a pipeline that logs requests.
+  final handler = Pipeline().addMiddleware(logRequests()).addHandler(_router);
+
+  // For running in containers, we respect the PORT environment variable.
+  final port = int.parse(Platform.environment['PORT'] ?? '8080');
+  final server = await serve(handler, ip, port);
+  print('Server listening on port ${server.port}');
+}