Add game tab to options menu, fix focus of GUI elements, add Delete option for save file

Zennysoft.Game.Godot.Implementation/Save/SaveFileManager.cs

@@ -74,4 +74,8 @@ public class SaveFileManager : ISaveFileManager
     var json = JsonSerializer.Serialize(gameData, jsonOptions);
     await _fileSystem.File.WriteAllTextAsync(filePath, json);
   }
+
+  public void DeleteSaveData() => DeleteSaveData(_defaultSaveLocation);
+
+  public void DeleteSaveData(string filePath) => _fileSystem.File.Delete(filePath);
 }