ammo system

* heads have abilities
* health and ammo shows in ui

src/npc.rs

@@ -1,5 +1,5 @@
 use crate::{
-    GameState, heads_ui::HEAD_COUNT, keys::KeySpawn, player::head_id_to_str, sounds::PlaySound,
+    GameState, active_heads::HEAD_COUNT, keys::KeySpawn, player::head_id_to_str, sounds::PlaySound,
     tb_entities::EnemySpawn,
 };
 use bevy::prelude::*;