handle a case, when start bottom nav position != 0

[nazariyshkarlat]

I propose to have an opportunity to set a start bottom navigation page. also, I added setPrimaryNavigationFragment(navHostFragment) (line 220) to correctly handle onBackPressed() on this start page.

[vipulasri]

@nazariyshkarlat is there a special case that brings out the possibility of using another position as initial?

[amit7127]

I have a requirement for setting the 3rd menu as the default menu when the app is opened.

But in @nazariyshkarlat solution, the First fragment is opening and then switching to the default fragment. So the solution is not so elegant.