Added Mention.User(GlobalUser)

src/Discord.Net/Helpers/Mention.cs

@@ -13,6 +13,9 @@ namespace Discord
 		/// <summary> Returns the string used to create a user mention. </summary>
 		public static string User(User user)
 			=> $"<@{user.Id}>";
+		/// <summary> Returns the string used to create a user mention. </summary>
+		public static string User(GlobalUser user)
+			=> $"<@{user.Id}>";
 		/// <summary> Returns the string used to create a channel mention. </summary>
 		public static string Channel(Channel channel)
 			=> $"<#{channel.Id}>";