add custom children description in README

Author: Alberto Dallaporta

README.md

@@ -19,7 +19,8 @@ This module wants to provide a stable and performing solution for maps clusterin
 
 **NOTES:**
 
-* the prop `key` of the markers rendered through `renderMarker` should not be left up to React. Instead, we strongly suggest to use an `id` in order the have unique keys while still taking advantage of React's recycling.
+* the prop `key` of the markers rendered through `renderMarker` should not be left up to React. Instead, we strongly suggest to use an `id` in order the have unique keys while still taking advantage of React's recycling
+* `ClusteredMapView` supports usual React children. Those children **won't be affected by clustering**, i.e. the behavior for those children is exactly the same as wrapping them around an [AirBnB's react-native-maps](https://github.com/airbnb/react-native-maps) instance
 
 ```JSX
 import React, { Component } from 'react'