Improve documentation for fitToCoordinates (react-native-maps#1037)

* added notes for fitToCoordinates call

* Notes for fitToCoordinates set in correct box

Author: Alvaro

docs/mapview.md

@@ -57,9 +57,9 @@
 |---|---|---|
 | `animateToRegion` | `region: Region`, `duration: Number` |
 | `animateToCoordinate` | `coordinate: LatLng`, `duration: Number` |
-| `fitToElements` | `animated: Boolean` |
+| `fitToElements` | `animated: Boolean` | 
 | `fitToSuppliedMarkers` | `markerIDs: String[]`, `animated: Boolean` | If you need to use this in `ComponentDidMount`, make sure you put it in a timeout or it will cause performance problems.
-| `fitToCoordinates` | `coordinates: Array<LatLng>, options: { edgePadding: EdgePadding, animated: Boolean }` |
+| `fitToCoordinates` | `coordinates: Array<LatLng>, options: { edgePadding: EdgePadding, animated: Boolean }` | If called in `ComponentDidMount` in android, it will cause an exception. It is recommended to call it from the MapView `onLayout` event.