Update links Navigation Routing (#2617)

*Formatting markdown provide a link to docs.*

## Pre-launch Checklist

- [x] I read the [Flutter Style Guide] _recently_, and have followed its
advice.
- [x] I signed the [CLA].
- [x] I read the [Contributors Guide].
- [ ] I have added sample code updates to the [changelog].
- [ ] I updated/added relevant documentation (doc comments with `///`).


If you need help, consider asking for advice on the #hackers-devrel
channel on [Discord].

<!-- Links -->
[Flutter Style Guide]:
https://github.com/flutter/flutter/blob/master/docs/contributing/Style-guide-for-Flutter-repo.md
[CLA]: https://cla.developers.google.com/
[Discord]:
https://github.com/flutter/flutter/blob/master/docs/contributing/Chat.md
[Contributors Guide]:
https://github.com/flutter/samples/blob/main/CONTRIBUTING.md
[changelog]: ../CHANGELOG.md

navigation_and_routing/README.md

@@ -1,12 +1,12 @@
 # Navigation and Routing
-A sample that shows how to use [go_router][https://pub.dev/packages/go_router]
+A sample that shows how to use [go_router](https://pub.dev/packages/go_router)
 API to handle common navigation scenarios.
 
 ## Goals
 - Demonstrate common navigation scenarios:
-  - Parsing path parameters ('/user/:id')
+  - Parsing path parameters (`/user/:id`)
   - Sign in (redirection)
   - Nested navigation using ShellRoute
-- Demonstrate how [deep linking][] is configured on iOS and Android
+- Demonstrate how [deep linking](https://docs.flutter.dev/ui/navigation/deep-linking#get-started) is configured on iOS and Android
 - Demonstrate how to use the Link widget from `package:url_Launcher` with the
   Router API.