v2.1.0 of flutter_device_compass

A Flutter compass plugin using device sensors. Heading is 0-360 degrees (0 = north). Changelog excerpt: - **Android:** - Fix fatal crash on `NaN`rotation-vector sensor samples by skipping non-finite samples before calculating azimuth ([#1](https://github.com/nafiskabbo/flutter_device_compass/pull/1)by [@mrweiland](https://github.com/mrweiland)). - Fix potential `NullPointerException`on…