Location provider

[david-rhodes]

Added a new example scene LocationProvider.unity and relevant LocationProvider scripts meant to show how to :

• Build a map for your current (device) location
• Update a virtual player's position and rotation based on a real or mock location and heading
• Use mock location providers to test in the Unity editor
• Convert between unity world space<—>earth space (latitude, longitude)

Added relevant in-line documentation and notes here: https://mapbox.github.io/mapbox-unity-sdk/docs/03-examples.html#locationprovider.

This was a common request from users and most of the work was already done for MapboxGO.

[isiyu]

Looks good @david-rhodes! - tested locally. Approving, just have thoughts on documentation - that don't block merging the PR.

The example description took some close reading to figure out what was happening. This example deals with things in action. I think this example would benefit from a vid cap when we start doing those, or some gifs.
https://mapbox.github.io/mapbox-unity-sdk/docs/03-examples.html#locationprovider

Inline code examples would be helpful for the location provider library.
https://mapbox.github.io/mapbox-unity-sdk/api/unity/Mapbox.Unity.Location.DeviceLocationProvider.html