settings_menu: Create a dedicated class for the settings

includes/rules.hpp

@@ -2,7 +2,7 @@
 * File name: rules.hpp
 * Author: lejulien
 * Date created: 09-01-2026 23:59:55
-* Date modified: 10-01-2026 21:49:44
+// Date modified: 12-01-2026 21:58:17
 * ------
 */
 
@@ -19,12 +19,12 @@ private:
 
 public:
   Rules();
-  void setup(World *world);
-  void newWorld(World *world);
+  void setup(std::shared_ptr<World> world);
+  void newWorld(std::shared_ptr<World> world);
   void update();
 
 private:
-  World *_world;
+  std::shared_ptr<World> _world;
   std::vector<bool> _buffer;
   int _width;
   int _height;