add: pistol weapon and enemy

Assets/Scripts/Enemy.cs

@@ -0,0 +1,12 @@
+using UnityEditor.Embree;
+using UnityEngine;
+
+public class Enemy : MonoBehaviour
+{
+    public float hp = 100f;
+
+    public void DealDamage(float damage) {
+        hp -= damage;
+        if (hp <= 0) Destroy(gameObject);
+    }
+}