Add boilerplate test

Summary: To verify that the infra is working.

Reviewed By: mweststrate

Differential Revision: D19881083

fbshipit-source-id: 92d5f55ecbef84003b6000b4c95df1fe0518719c

pkg/src/__tests__/index.ts

@@ -0,0 +1,12 @@
+/**
+ * Copyright (c) Facebook, Inc. and its affiliates.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ *
+ * @format
+ */
+
+test('tests are working', () => {
+  expect(true).toBeTruthy();
+});