Fix README examples app url

Close necolas#2338

Author: necolas

packages/react-native-web/README.md

@@ -10,7 +10,7 @@ The [documentation site](https://necolas.github.io/react-native-web/) ([source](
 
 ## Example
 
-The [examples app](https://pk4zn6v4o0.sse.codesandbox.io/) ([source](https://github.com/necolas/react-native-web/blob/master/packages/react-native-web-examples)) demonstrates many available features. Fork the [codesandbox](https://codesandbox.io/s/github/necolas/react-native-web/tree/master/packages/react-native-web-examples) to make changes and see the results.
+The [examples app](https://p9t5cp.sse.codesandbox.io/) ([source](https://github.com/necolas/react-native-web/blob/master/packages/react-native-web-examples)) demonstrates many available features. Fork the [codesandbox](https://codesandbox.io/s/github/necolas/react-native-web/tree/master/packages/react-native-web-examples) to make changes and see the results.
 
 You'll notice that there is no reference to `react-dom` in components. The `App` component that is shown below is defined using the APIs and Components of React Native, but it can also be rendered on the web using React Native for Web.