Deeplink page is not library agnostic

### Page URL

https://docs.flutter.dev/cookbook/navigation/set-up-app-links/

### Page source

https://github.com/flutter/website/tree/main/src/content/cookbook/navigation/set-up-app-links.md

### Describe the problem

This page describes how to set up deep linking in your app, but only if you use the GoRouter library. I think this page should be expanded to include deeplinking without GoRouter.

### Expected fix

I would love to write up a guide myself, but as of yet I still do not know how to handle deeplinks without GoRouter because every guide out there, including this one, only provides a implementation that relies on GoRouter. It's very frustrating.

### Additional context

_No response_

### I would like to fix this problem.

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