Update the Emoji API model to add User? attribute

src/Discord.Net.Rest/API/Common/Emoji.cs

@@ -1,4 +1,4 @@
-#pragma warning disable CS1591
+#pragma warning disable CS1591
 using Newtonsoft.Json;
 
 namespace Discord.API
@@ -17,5 +17,7 @@ namespace Discord.API
         public bool RequireColons { get; set; }
         [JsonProperty("managed")]
         public bool Managed { get; set; }
+        [JsonProperty("user")]
+        public Optional<User> User { get; set; }
     }
 }