title: Can a stack navigator have 2 different routes in react navigation
body: <p>My project structure looks like this :</p>
  
  <pre><code>Tab navigator
  |-Tab1
  |-Tab2
      |-stack navigator
            |-login
                |
               screen1
                |
               screen2
                 |
               screen3
  |-Tab3
  |-Tab4
  </code></pre>
  
  <p>I want my stack navigator route to start from screen1 once I enter the username and password for login screen. Is there any way we can achieve this?
  Can we reroute/change the routes of stack navigator?</p>