Navigation example with multiple activities

[PatrickKuijpers]

Having a sample project showing navigation for multiple activities would be really helpful. Right now there are only examples for single activity navigation. For example, NavigationBasicSample could be created with a separate activity for leaderboards (2 fragments) and matches (4 fragments).

This would strongly support the documentation of how to migrate old activity navigation to the new androidx navigation.

[PatrickKuijpers]

It would be great if conditional navigation could also be added to this example. eg. register required only once. If registered, then directly start a match and skip the register screen.