Web should be included as an add-to-app platform in the docs

[jmagman]

What information needs to be added?

https://docs.flutter.dev/platform-integration/web/embedding-flutter-web exists, but it's not clear in the docs that it's spiritually the same concept as add-to-app (even though it is linked from Add to an existing app > Add to a web app menu).

The docs should be changed to reflect that an existing web app can incrementally add Flutter, not just iOS and Android.

Where should this new content appear?

https://docs.flutter.dev/add-to-app https://docs.flutter.dev/add-to-app/debugging https://docs.flutter.dev/add-to-app/multiple-flutters https://docs.flutter.dev/add-to-app/performance

I would like to fix this problem.

• [ ] I will try and fix this problem on docs.flutter.dev.