Add an Inventory and Backpack System

Add a limited-capacity inventory system for managing weapons, ammunition, healing supplies, armor, and other equipment. A grid-based layout similar to Resident Evil could require players to arrange items and prioritize what they carry. Equipped items could be assigned to quick-access slots, while additional weapons and equipment would need to be selected manually from the inventory. This system would be particularly suitable for Zombies, survival, or extraction-style game modes.