Document annotationView coordinate setting behavior during dragging

[samfader]

When using setDragState to drag an annotation, we should note that the center coordinates of the annotation is set only once the dragState of the annotationView has been set to MGLAnnotationViewDragStateEnding. You can see this here. Therefore, these coordinates should not be relied on for, for example, drawing a line between a "static" annotation and an annotation that is being dragged in real time.

We should document this behavior and/or create an example showing best practices for dragging annotations and using that drag to update other geometries on the map.

cc @jmkiley @nishant-karajgikar

[jmkiley]

Perfect, thanks! We currently have a basic example for draggable annotation views, but we could likely add something to either that example or to iosapp to show best practices.

[knov]

cc @mapbox/maps-ios