add: Template for Save and config

src/PoloniumRegistry.cs

@@ -0,0 +1,19 @@
+using Godot;
+using Polonium.Resources;
+using Polonium.Scenes;
+
+namespace Polonium;
+
+public class PoloniumRegistry
+{
+    private static PoloniumRegistry InternalInstance { get; set; }
+    public static PoloniumRegistry Instance => InternalInstance ??= new PoloniumRegistry();
+    public RootScene RootScene { get; set; }
+    public Config Config { get; set; }
+    public Save Save { get; set; }
+
+    public static void Prepare()
+    {
+        DirAccess.MakeDirAbsolute("user://saves");
+    }
+}