Add Smoothing to CameraFollow script (#4422)

* update cam script & add comments

* use fixedDeltaTime in SmoothDamp

Project/Assets/ML-Agents/Examples/SharedAssets/Scripts/CameraFollow.cs

 {
     public class CameraFollow : MonoBehaviour
     {
-        public Transform target;
-        Vector3 m_Offset;
+        [Tooltip("The target to follow")] public Transform target;
+
+        [Tooltip("The time it takes to move to the new position")]
+        public float smoothingTime; //The time it takes to move to the new position
+
+        private Vector3 m_Offset;
+        private Vector3 m_CamVelocity; //Camera's velocity (used by SmoothDamp)
 
         // Use this for initialization
         void Start()
 
-        // Update is called once per frame
-        void Update()
+        void FixedUpdate()
-            // gameObject.transform.position = target.position + offset;
-            gameObject.transform.position = newPosition;
+
+            gameObject.transform.position =
+                Vector3.SmoothDamp(transform.position, newPosition, ref m_CamVelocity, smoothingTime, Mathf.Infinity,
+                    Time.fixedDeltaTime);
         }
     }
 }