chore: Add user agent to .sdk_metadata.json (#293)

Author: kinyoklion

.sdk_metadata.json

@@ -6,7 +6,8 @@
       "type": "client-side",
       "languages": [
         "Java", "Kotlin"
-      ]
+      ],
+      "userAgents": ["AndroidClient"]
     }
   }
 }