Support 3D follow

**Is your feature request related to a problem? Please describe.**

It would be nice to have a feature in the library that developers can turn on or off that would have the map camera automatically follow the user's location on the map in 3D - something like this:


**Describe the solution you'd like**

Moving and tilting the map camera based on rotation vector sensors is described in this Google I/O video (including sample code), which the above screenshot is grabbed from:
https://youtu.be/_oZiK_NJuG8?t=1453

I've implemented a version of this in an app I maintain:
https://github.com/barbeau/gpstest/blob/master/GPSTest/src/google/java/com/android/gpstest/GpsMapFragment.java#L281

Exact API design is TBD.

**Describe alternatives you've considered**
Do nothing - don't implement the feature

**Additional context**
See links above

Start by reviewing the linked Google I/O video and the referenced GPSTest GpsMapFragment.java implementation around line 281. Then inspect this library's map-camera entry points to determine where a configurable 3D follow feature could fit. Done requires an agreed API design and a working camera-follow implementation with appropriate tests or validation.

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