Tracking interactions

Summary:
Set up basic primitives for user interaction tracking. I hope the docs and unit tests in this diff are self explanatory :)

In upcoming diffs:
* Wire up to scuba events
* Annotate all important parts of Flipper Chrome
* Investigate if we can wrap important interactions of ANT by default

Reviewed By: jknoxville

Differential Revision: D25120234

fbshipit-source-id: 9849d565d7be27e498cc2b4db33e7d6e6938ee06

desktop/flipper-plugin/src/utils/sleep.tsx

@@ -0,0 +1,14 @@
+/**
+ * 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
+ */
+
+export async function sleep(ms: number): Promise<void> {
+  return new Promise((resolve) => {
+    setTimeout(resolve, ms);
+  });
+}