Example for custom location manager

Currently, the navigation SDK documentation for iOS doesn't have a guide for device location like Android does since device location and location management usually works by default on iOS. However, to get closer to documentation parity, a guide or example could be helpful. It would be challenging to find enough information to fill an iOS location guide, but an example could be useful.

A new example for creating a custom location manager would also be helpful for cleaning up locations outside of turn-by-turn navigation, debugging, and simulation.

Start by reviewing the existing iOS examples and the Android device-location guide referenced in the issue. Define the scope of a custom location manager example that covers location cleanup outside turn-by-turn navigation, debugging, and simulation; done means the example and its accompanying guidance provide useful iOS documentation parity.