This is a non-breaking change following suggestions from @arriolac for addressing googlemaps#149: googlemaps#150 (comment)

This PR does not add an `onDrag` callback parameter to `Marker()`, which would be a somewhat breaking change; this functionality is not strictly necessary and I see alternatives that may be preferable.

Summary of changes:

1. Deprecate MarkerState.dragState and DragState enum. These were carried over from GoogleMap SDK; they are events that were mischaracterized as states.
2. Replace with MarkerState.isDragging boolean.
3. Clarify KDoc in several places.
4. Add several examples providing patterns for common use cases.
5. Organize Marker-related examples into their own folder.

Fixes googlemaps#149

…States from a changing model list of marker positions by collecting results from key() composable

Rename marker examples folder to markerexamples for clarity