fix(instructions): react-hooks 02.01 (#239)

* fix(instructions): react-hooks 02.01

Exercise `react-hooks/exercises/02.side-effects/01.problem.effects/index.tsx`

The current instructions don't make sense... this patch clears things up.

* fix(instructions): Explain that react-hooks 02.01 should be broken

> in the useEffect callback, subscribe to window's popstate event

If a dev knows how to use `useEffect()` this will look like a bug... because it is. Let's explain that this bug is supposed to be here at this point.

* Apply suggestions from code review

---------

Co-authored-by: Kent C. Dodds <[email protected]>

Author: MikeRatcliffe

exercises/02.side-effects/01.problem.effects/index.tsx

@@ -19,6 +19,7 @@ function App() {
 
 	// 🐨 add a useEffect(() => {}, []) call here (we'll talk about that empty array later)
 	// 🐨 in the useEffect callback, subscribe to window's popstate event
+	// 🦉 if that doesn't make sense to you... don't worry, it's supposed to be broken! We'll fix it next
 	// 🐨 your event handler should call setQuery to getQueryParam()
 	// 📜 https://developer.mozilla.org/en-US/docs/Web/API/EventTarget/addEventListener