Try to 'add' Fragments instead of 'replace' when using Jetpack's Navigation

[nicoqueijo]

Try to see if I could ‘add’ instead of ‘replace’ the SelectorFragment when I click on the FloatingActionButton so that WatchlistFragment stays in memory.

The default behavior when using Jetpack’s Navigation is to 'replace' and that is why I always have to redraw the DragLinearLayout when we return from SelectorFragment.

If I could do an ‘add’ instead of a ‘replace’ then this would provide a much better UX as there would be no overhead cost when returning from selecting a Currency.