Add ammo consumption and item pickup systems

GameCore/Events/ItemPickupAttemptEvent.cs

@@ -0,0 +1,17 @@
+using GameCore.ECS;
+using GameCore.Events.Interfaces;
+
+namespace GameCore.Events;
+
+public readonly struct ItemPickupAttemptEvent(
+    Entity picker,
+    Entity itemEntity,
+    string itemId,
+    int quantity
+) : IEvent
+{
+    public readonly Entity Picker = picker;
+    public readonly Entity ItemEntity = itemEntity;
+    public readonly string ItemId = itemId;
+    public readonly int Quantity = quantity;
+}