Add player controller, state management, and input handling

- Implemented PlayerController.cs to manage player movement and actions.
- Created PlayerState.cs to track player lives, coins, and key status.
- Added CameraFollow.cs for smooth camera movement following the player.
- Developed Character.cs as an abstract class for character behavior.
- Introduced Enums.cs for defining TreasureType and MapElementType.
- Added IDoor interface for door interactions.
- Created InputActions.cs for handling player input actions.
- Implemented MainMenu.cs for basic menu functionality including play and exit options.

Assets/Scripts/Environment/MapElements/MapElementSO.cs

@@ -0,0 +1,7 @@
+using UnityEngine;
+
+[CreateAssetMenu()]
+public class MapElementSO : ScriptableObject
+{
+    public MapElementType ElementType;
+}