Added ratbot enemies that move towards the player

Assets/Ratbot.cs

@@ -0,0 +1,20 @@
+using UnityEngine;
+
+public class Ratbot : MonoBehaviour
+{
+	public float moveSpeed;
+	GameObject player;
+    // Start is called once before the first execution of Update after the MonoBehaviour is created
+    void Start()
+    {
+		player = GameObject.FindGameObjectWithTag("Player");
+    }
+
+    // Update is called once per frame
+    void Update()
+    {
+		Rigidbody2D controller = GetComponent<Rigidbody2D>();
+		Vector2 direction = (player.transform.position - transform.position).normalized;
+		controller.linearVelocity = direction*moveSpeed;
+    }
+}