Move save logic out of Game

Zennysoft.Game.Abstractions/Save/ISaveFileManager.cs

@@ -0,0 +1,10 @@
+using System.Text.Json;
+
+namespace Zennysoft.Game.Abstractions;
+
+public interface ISaveFileManager<T>
+{
+  public Task WriteToFile(T gameData);
+
+  public Task<T> ReadFromFile();
+}