* Add external components e2e, resolve navigationItem from external component

* Update ExternalComponent.test.js

* Update ExternalComponent.test.js

* Fix lint

Add iOS support for `bottomTabs.attachMode`.
This property controls when BottomTabs children are attached to hierarchy and when their React views are created.

By default, RNN attaches all children at the same time which might impact loading time as a few screens are instantiated at once.
Using `afterInitialTab` or `onSwitchToTab` generally leads to improved start up time.