Small bugfix in hangman, thx ala

src/NadekoBot/Modules/Games/Common/Hangman/HangmanGame.cs

@@ -1,4 +1,4 @@
-#nullable disable
+#nullable disable
 using AngleSharp.Text;
 
 namespace NadekoBot.Modules.Games.Hangman;
@@ -103,6 +103,7 @@ public sealed class HangmanGame
                 return GetState(GuessResult.Win);
             }
 
+            _correct.Add(charGuess);
             return GetState(GuessResult.Guess);
         }