Add ammo consumption and item pickup systems

GameCore/Combat/WeaponSystem.cs

@@ -27,12 +27,21 @@ public class WeaponSystem : ISystem
 
             if (input.IsFiring && weapon.CooldownTimer <= 0f)
             {
-                // Check for ammo if applicable
-                
                 var context = new EffectContext { World = world, Owner = entity };
 
-                foreach (var effect in weapon.OnFireEffects) effect.Execute(context);
+                var canFire = true;
+                foreach (var cost in weapon.FireCosts)
+                    if (!cost.CanAfford(context))
+                    {
+                        canFire = false;
+                        //TODO: Publish an event or notify the player they can't fire
+                        break;
+                    }
 
+                if (!canFire) continue;
+
+                foreach (var cost in weapon.FireCosts) cost.Execute(context);
+                foreach (var effect in weapon.OnFireEffects) effect.Execute(context);
                 world.PublishEvent(new WeaponFiredEvent(entity, input.MuzzlePosition));
                 weapon.CooldownTimer = 1f / weapon.FireRate;
             }