make sure plugins can be loaded into Flipper

Summary: Make sure Sandy plugins are loaded properly from disk

Reviewed By: jknoxville

Differential Revision: D22186275

fbshipit-source-id: fd2f560a7bed959b18e05db2a087909ad876ab9d

desktop/app/src/dispatcher/__tests__/SandyTestPlugin.tsx

@@ -0,0 +1,24 @@
+/**
+ * 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
+ */
+
+import * as React from 'react';
+
+import {FlipperClient} from 'flipper-plugin';
+
+type Events = {
+  inc: {delta: number};
+};
+
+export function plugin(_client: FlipperClient<Events, {}>) {
+  return {};
+}
+
+export function Component() {
+  return <h1>Sandy high fives Flipper</h1>;
+}