add pinned property in comment

osu.Game/Online/API/Requests/Responses/Comment.cs

@@ -58,6 +58,9 @@ namespace osu.Game.Online.API.Requests.Responses
         [JsonProperty(@"edited_by_id")]
         public long? EditedById { get; set; }
 
+        [JsonProperty(@"pinned")]
+        public bool Pinned { get; set; }
+
         public User EditedUser { get; set; }
 
         public bool IsTopLevel => !ParentId.HasValue;