Implement a "FreeLook view"

Hi, i would customize this script that is a simple mouse look+smoothing. I'm trying to add a freelook view which allow me to look around world when i press a Button.

 using UnityEngine;
  
 // Very simple smooth mouselook modifier for the MainCamera in Unity
 // by Francis R. Griffiths-Keam - www.runningdimensions.com 
  
 [AddComponentMenu("Camera/Simple Smooth Mouse Look ")]
 public class SimpleSmoothMouseLook : MonoBehaviour
 {
     Vector2 _mouseAbsolute;
     Vector2 _smoothMouse;
  
     public Vector2 clampInDegrees = new Vector2(360, 180);
     public bool lockCursor;
     public Vector2 sensitivity = new Vector2(2, 2);
     public Vector2 smoothing = new Vector2(3, 3);
     public Vector2 targetDirection;
     public Vector2 targetCharacterDirection;
  
     // Assign this if there's a parent object controlling motion, such as a Character Controller. 
     // Yaw rotation will affect this object instead of the camera if set.
     public GameObject characterBody;
  
     void Start()
     {
         // Set target direction to the camera's initial orientation.
         targetDirection = transform.localRotation.eulerAngles;
  
         // Set target direction for the character body to its inital state.
         if (characterBody) targetCharacterDirection = characterBody.transform.localRotation.eulerAngles;
     }
  
     void Update()
     {
         // Ensure the cursor is always locked when set
         Screen.lockCursor = lockCursor;
  
         // Allow the script to clamp based on a desired target value.
         var targetOrientation = Quaternion.Euler(targetDirection);
         var targetCharacterOrientation = Quaternion.Euler(targetCharacterDirection);
  
         // Get raw mouse input for a cleaner reading on more sensitive mice.
         var mouseDelta = new Vector2(Input.GetAxisRaw("Mouse X"), Input.GetAxisRaw("Mouse Y"));
  
         // Scale input against the sensitivity setting and multiply that against the smoothing value.
         mouseDelta = Vector2.Scale(mouseDelta, new Vector2(sensitivity.x * smoothing.x, sensitivity.y * smoothing.y));
  
         // Interpolate mouse movement over time to apply smoothing delta.
         _smoothMouse.x = Mathf.Lerp(_smoothMouse.x, mouseDelta.x, 1f / smoothing.x);
         _smoothMouse.y = Mathf.Lerp(_smoothMouse.y, mouseDelta.y, 1f / smoothing.y);
  
         // Find the absolute mouse movement value from point zero.
         _mouseAbsolute += _smoothMouse;
  
         // Clamp and apply the local x value first, so as not to be affected by world transforms.
         if (clampInDegrees.x < 360)
             _mouseAbsolute.x = Mathf.Clamp(_mouseAbsolute.x, -clampInDegrees.x * 0.5f, clampInDegrees.x * 0.5f);
  
         var xRotation = Quaternion.AngleAxis(-_mouseAbsolute.y, targetOrientation * Vector3.right);
         transform.localRotation = xRotation;
  
         // Then clamp and apply the global y value.
         if (clampInDegrees.y < 360)
             _mouseAbsolute.y = Mathf.Clamp(_mouseAbsolute.y, -clampInDegrees.y * 0.5f, clampInDegrees.y * 0.5f);
  
         transform.localRotation *= targetOrientation;
  
         // If there's a character body that acts as a parent to the camera
         if (characterBody)
         {
             var yRotation = Quaternion.AngleAxis(_mouseAbsolute.x, characterBody.transform.up);
             characterBody.transform.localRotation = yRotation;
             characterBody.transform.localRotation *= targetCharacterOrientation;
         }
         else
         {
             var yRotation = Quaternion.AngleAxis(_mouseAbsolute.x, transform.InverseTransformDirection(Vector3.up));
             transform.localRotation *= yRotation;
         }
     }
 }

So, how i can implement a free look view?

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