Add Resume/Exit buttons to pause menu, handle logic for returning to main menu and starting a new game

Zennysoft.Game.Ma.Implementation/Game/state/GameState.Output.cs

@@ -6,6 +6,8 @@ public partial class GameState
   {
     public readonly record struct InitializeGame;
 
+    public readonly record struct ExitGame;
+
     public readonly record struct LoadGameFromFile;
 
     public readonly record struct OpenInventoryMenu;