add: pistol weapon and enemy

Assets/Scripts/BulletProjectile.cs

@@ -0,0 +1,30 @@
+using UnityEngine;
+
+public class BulletProjectile : MonoBehaviour
+{
+    public float speed = 1f;
+    public float damage = 20f;
+    public float timeToLive = 5f;
+
+    float currentTime = 0;
+
+    Rigidbody rb;
+
+    void Start() {
+        rb = GetComponent<Rigidbody>();
+        rb.linearVelocity = transform.forward * speed;
+    }
+
+    void Update() {
+        currentTime += Time.deltaTime;
+        if (currentTime >= timeToLive) Destroy(gameObject);
+    }
+
+    void OnTriggerEnter(Collider other) {
+        if (other.gameObject.CompareTag("Enemy")) {
+            Enemy enemy = other.GetComponent<Enemy>();
+            enemy.DealDamage(damage);
+        }
+        Destroy(gameObject);
+    }
+}