Update 02.md

Closes #1

src/exercise/02.md

@@ -112,7 +112,9 @@ run all your profiling on that. Compare it to before. MUCH faster right!?
 > Warning, this one's _really_ cool, but kinda tricky... Also, the intent isn't
 > necessarily for you to learn web workers, but just to expose you to a good use
 > case for them. You can get started learning about web workers here:
-> https://kentcdodds.com/blog/speed-up-your-app-with-web-workers
+> [Speed up your App with Web Workers](https://kentcdodds.com/blog/speed-up-your-app-with-web-workers).
+> Additionally, sometimes this step doesn't seem to work during development due
+> to [dependency issues](https://github.com/kentcdodds/react-performance/issues/1).
 
 It's awesome that we reduced how often we have to call `getItems`,
 unfortunately, on low-powered devices, `getItems` is still quite slow when it
@@ -138,6 +140,10 @@ you'll want to run the DevTools profiler on the production build of the app. Run
 `npm run build` and `npm run serve`. Remember that you'll need to rerun the
 build every time you make a change.
 
+<callout-warning>
+
+</callout-warning>
+
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