Add map loading logic and spawn rate control

Zennysoft.Game.Ma/addons/dungeon_floor_layout/DungeonFloorLayoutNode.cs

@@ -0,0 +1,22 @@
+#if TOOLS
+using Godot;
+using Zennysoft.Game.Ma;
+
+[Tool]
+public partial class DungeonFloorLayoutNode : EditorPlugin
+{
+  public override void _EnterTree()
+  {
+    // Initialization of the plugin goes here.
+    var script = GD.Load<Script>("res://addons/dungeon_floor_layout/DungeonFloorLayout.cs");
+    var texture = GD.Load<Texture2D>("res://addons/dungeon_floor_layout/icon_door.png");
+    AddCustomType(nameof(DungeonFloorLayout), nameof(LayoutType), script, texture);
+  }
+
+  public override void _ExitTree()
+  {
+    // Clean-up of the plugin goes here.
+    RemoveCustomType(nameof(DungeonFloorLayout));
+  }
+}
+#endif