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/test/server_test.dart

@@ -0,0 +1,50 @@
+import 'dart:convert';
+import 'dart:io';
+
+import 'package:http/http.dart';
+import 'package:test/test.dart';
+
+// Manual test:
+// $ dart bin/server.dart
+// $ curl -X POST -d '{"by": 1}' -H "Content-Type: application/json" localhost:8080/
+
+void main() {
+  final port = '8080';
+  final host = 'http://0.0.0.0:$port';
+  late Process p;
+
+  group(
+    'Integration test should',
+    () {
+      setUp(() async {
+        p = await Process.start(
+          'dart',
+          ['run', 'bin/server.dart'],
+          environment: {'PORT': port},
+        );
+        // Wait for server to start and print to stdout.
+        await p.stdout.first;
+      });
+
+      tearDown(() => p.kill());
+
+      test('Increment', () async {
+        final response = await post(Uri.parse('$host/'), body: '{"by": 1}');
+        expect(response.statusCode, 200);
+        expect(response.body, '{"value":1}');
+      });
+
+      test('Get', () async {
+        final response = await get(Uri.parse('$host/'));
+        expect(response.statusCode, 200);
+        final resp = json.decode(response.body) as Map;
+        expect(resp.containsKey('value'), true);
+      });
+    },
+    onPlatform: <String, dynamic>{
+      'windows': [
+        Skip('Failing on Windows CI'),
+      ]
+    },
+  );
+}