Implemented pull request review comments API

Octokit/Models/Request/PullRequestReviewCommentReplyCreate.cs

@@ -0,0 +1,18 @@
+using Octokit.Internal;
+
+namespace Octokit
+{
+    public class PullRequestReviewCommentReplyCreate : RequestParameters
+    {
+        /// <summary>
+        /// The text of the comment.
+        /// </summary>
+        public string Body { get; set; }
+
+        /// <summary>
+        /// The comment Id to reply to.
+        /// </summary>
+        [Parameter(Key = "in_reply_to")]
+        public int InReplyTo { get; set; }
+    }
+}