Incorrect reference to styles.css

https://github.com/FirebaseExtended/firebase-video-samples/blob/71e7e607624492f4cfb3b7d4f3e05618dd093267/fundamentals/getting-started-with-auth-web/src/index.html#L9

This file is not generated/copied to dist/ by webpack.
The actual use of the file is through the import in index.js, and the content to merged in bundle.js