add: pistol weapon and enemy

Assets/Scripts/Weapon.cs

@@ -0,0 +1,13 @@
+using UnityEngine;
+
+public abstract class Weapon : MonoBehaviour
+{
+    public bool isActive { get; private set; } = true;
+
+    public abstract void Shoot(bool keyDown, bool keyHold);
+
+    public void SetWeaponState(bool active) {
+        isActive = active;
+        GetComponent<MeshRenderer>().enabled = active;
+    }
+}