feat(EntityBase): 添加死亡时掉落灵魂物品的功能

在实体死亡时，除了原有掉落物外，现在会额外生成1-2个灵魂物品

scripts/Statemachine/EntityBase.gd

@@ -321,6 +321,11 @@ func tryDie(by: BulletBase = null):
 			fields[FieldStore.Entity.MAX_HEALTH] * randf_range(1 - GameRule.beachballOffset, 1 + GameRule.beachballOffset),
 			position + MathTool.randv2_range(GameRule.itemDroppedSpawnOffset)
 		)
+		ItemDropped.generate(
+			ItemStore.ItemType.SOUL,
+			randi_range(1, 2),
+			position + MathTool.randv2_range(GameRule.itemDroppedSpawnOffset)
+		)
 		if isPlayer():
 			if UIState.player == self:
 				UIState.setPanel("GameOver", [displayName, by.launcher.displayName, by.displayName])