Migrate React example app to react-scripts 5

Reviewed By: antonk52

Differential Revision: D35114197

fbshipit-source-id: 88b35b4d927d7eca099a62d9cf4319ffe3ecf423

js/react-flipper-example/src/setupTests.ts

@@ -0,0 +1,14 @@
+/**
+ * Copyright (c) Meta Platforms, Inc. and affiliates.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ *
+ * @format
+ */
+
+// jest-dom adds custom jest matchers for asserting on DOM nodes.
+// allows you to do things like:
+// expect(element).toHaveTextContent(/react/i)
+// learn more: https://github.com/testing-library/jest-dom
+import '@testing-library/jest-dom';