Add user avatar url to Contributor model (#23)

Program.cs

@@ -309,6 +309,7 @@ namespace dotnetthanks_loader
                             {
                                 Name = author.name,
                                 Link = author.html_url,
+                                Avatar = author.avatar_url,
                                 Count = 1
                             };
                             person.Repos.Add(new RepoItem() { Name = repoName, Count = 1 });

Release.cs

@@ -74,6 +74,7 @@ namespace dotnetthanks
     {
         public string Name { get; set; }
         public string Link { get; set; }
+        public string Avatar { get; set; }
         public int Count { get; set; }
 
         public List<RepoItem> Repos { get; set; } = new List<RepoItem>();