Deep link UDL - added a note

Per Slack: https://appsflyer.slack.com/archives/C5RDRS58X/p1723186908673099

doc/DeepLink.md

@@ -58,6 +58,10 @@ appsflyerSdk.onAppOpenAttribution((res){
 
 ###  <a id="unified-deeplinking"> 3. Unified deep linking
 
+> 📘 **UDL privacy protection**
+> 
+> For new users, the UDL method only returns parameters relevant to deferred deep linking: `deep_link_value` and `deep_link_sub1` to `deep_link_sub10`. If you try to get any other parameters (`media_source`, `campaign`, `af_sub1-5`, etc.), they return `null`.
+
 The flow works as follows:
 
 1. User clicks the OneLink short URL.