docs(firebase_dynamic_links): add deprecation note to README.md (#11506)

Author: nilsreichardt

packages/firebase_dynamic_links/firebase_dynamic_links/README.md

@@ -7,6 +7,8 @@ A Flutter plugin to use the [Firebase Dynamic Links API](https://firebase.google
 
 To learn more about Dynamic Links, please visit the [Firebase website](https://firebase.google.com/products/dynamic-links)
 
+> Deprecated: Firebase Dynamic Links is deprecated and should not be adopted in projects that don't already use it. The service will shut down on August 25, 2025. See the [Dynamic Links Deprecation FAQ](https://firebase.google.com/support/dynamic-links-faq) for more information.
+
 ## Getting Started
 
 To get started with Dynamic Links for Flutter, please [see the documentation](https://firebase.flutter.dev/docs/dynamic-links/overview).