Deprecate Dynamic Links

Author: morganchen12

dynamic_links/testapp/readme.md

@@ -1,6 +1,11 @@
 Firebase Dynamic Links Quickstart
 =================================
 
+> [!IMPORTANT]
+> Firebase Dynamic Links is **deprecated** and should not be used in new projects. The service will shut down on August 25, 2025.
+>
+> Please see our [Dynamic Links Deprecation FAQ documentation](https://firebase.google.com/support/dynamic-links-faq) for more guidance.
+
 The Firebase Dynamic Links Quickstart demonstrates logging a range
 of different events using the Firebase Dynamic Links C++ SDK.  The application
 has no user interface and simply logs actions it's performing to the console.