Fix docs typo (facebook#2420)

"ensuring that you web app" ->
"ensuring that your web app"

packages/react-scripts/template/README.md

@@ -1381,7 +1381,7 @@ and it will take care of generating a service worker file that will automaticall
 precache all of your local assets and keep them up to date as you deploy updates.
 The service worker will use a [cache-first strategy](https://developers.google.com/web/fundamentals/instant-and-offline/offline-cookbook/#cache-falling-back-to-network)
 for handling all requests for local assets, including the initial HTML, ensuring
-that you web app is reliably fast, even on a slow or unreliable network.
+that your web app is reliably fast, even on a slow or unreliable network.
 
 If you would prefer not to enable service workers prior to your initial
 production deployment, then remove the call to `serviceWorkerRegistration.register()`