title: How to change back button route in react navigation
body: <p>i am using react-navigation (stack-navigation). i want to change my header back button icon route.</p>
  
  <ol>
  <li>Home</li>
  <li>BookTicket</li>
  <li><p>MyBookings</p>
  
  <p>these are the screens i have in my project.Now when i click header back button in  MyBookings screen it should route to Home Screen.</p></li>
  </ol>