feat(ios,v10): add new Image component, to generate mapbox images using react-native

[mfazekas]

Introduce a new Image component to generate mapbox images using react-native views. It's v10 only and will not be implemented on other platforms. It's iOS only for now.

This means SVG or Skia, etc can used to generate symbols that appear on mapbox layers.

<Mapbox.Images>
  <Mapbox.Image name="rn-image" sdf>
    <View style={{backgroundColor:'red', width: 40, height: 40, borderRadius: 10}}></View>
  </Mapbox.Image>
</Mapbox.Images>

For stretching options see: mapbox/mapbox-gl-js#8917