A missing event state: comment_deleted (#1818)

* A missing event state: comment_deleted

Adding support for the comment_deleted event status.

* Add two new Event Status: Marked & Unmarked duplicates

* Update EventInfo.cs

Octokit/Models/Response/EventInfo.cs

@@ -272,6 +272,24 @@ namespace Octokit
         /// A commit comment was made.
         /// </summary>
         [Parameter(Value = "commit-commented")]
-        CommitCommented
+        CommitCommented,
+        
+        /// <summary>
+        /// A user with write permissions marked an issue as a duplicate of another issue or a pull request as a duplicate of another pull request.
+        /// </summary>
+        [Parameter(Value = "marked_as_duplicate")]
+        MarkedAsDuplicate,
+        
+        /// <summary>
+        /// An issue that a user had previously marked as a duplicate of another issue is no longer considered a duplicate.
+        /// </summary>
+        [Parameter(Value = "unmarked_as_duplicate")]
+        UnmarkedAsDuplicate,
+        
+        /// <summary>
+        /// An issue comment was deleted.
+        /// </summary>
+        [Parameter(Value = "comment_deleted")]
+        CommentDeleted
     }
 }