Load screens based on user auth status

NavigationSwitch.js

<NavigationContainer>
  <Stack.Navigator 
    headerMode="screen"
    screenOptions={{
      headerTintColor: 'white',
      headerStyle: styles.header,
    }}  
  >
    {this.state.isLoggedIn ? (
      <>
        <Stack.Screen name="Main" component={MainNavigator} 
        options={{ 
          headerShown:true,
          // title: 'My home',
          headerRight: () => (
            <View>
            <Button onPress={() => Auth.signOut({ global: true })}  transparent>
              <Icon type="FontAwesome" name="sign-out" style={{color: 'white'}}/>
            </Button>
            </View>
          )
        }}
        />
      </>
    ) : (
      <>
      <Stack.Screen name="Amplify Test" component={AuthTabs} 
        options={{ 
          headerShown:true
        }}
      />
      </>
    )}
  </Stack.Navigator>
</NavigationContainer>