Add Universal Links recommendation to the README (#908)

Author: Widcket

README.md

@@ -140,7 +140,9 @@ Go to the settings page of your [Auth0 application](https://manage.auth0.com/#/a
 
 > [!NOTE]
 > On iOS 17.4+ and macOS 14.4+ it is possible to use Universal Links as callback and logout URLs. When enabled, Auth0.swift will fall back to using a custom URL scheme on older iOS / macOS versions.
->
+> 
+> Whenever possible, Auth0 recommends using Universal Links as a secure way to link directly to content within your app. Custom URL schemes can be subject to [client impersonation attacks](https://datatracker.ietf.org/doc/html/rfc8252#section-8.6).
+> 
 > **This feature requires Xcode 15.3+ and a paid Apple Developer account**.
 
 ##### iOS