title: scrollToIndex() is not a function
body: <p>I have currently have a map and a carousel(similar to <code>FlatList</code>) and I want to be able to use <code>scrollToIndex</code> method of <code>FlatList</code> to snap to a certain item in the array. The issue is when I adopted the <a href="https://github.com/archriss/react-native-snap-carousel" rel="nofollow noreferrer">react-native-snap-carousel</a> library, which is based on <code>ScrollView</code>, I lost the ability to use the <code>scrollToIndex</code> method.  The ability to scroll to a certain index was working perfectly fine with <code>FlatList</code>. </p>
  
  <p>I'm using a functional component so I'm using the <code>useRef</code> hook:</p>
  
  <pre class="lang-js prettyprint-override"><code>    const flatListRef = useRef()
      const handleMarker = index =&gt; {
          flatListRef.current.scrollToIndex({ index, animated: true })
      }
  </code></pre>
  
  <p>I'm using <code>react-native-maps</code> for my map and the <code>handleMarker</code> above is so that when the user clicks on a marker on the map, the Carousel snaps to the pertaining item:</p>
  
  <pre class="lang-js prettyprint-override"><code>&lt;Marker
      key={marker.id}
      coordinate={{ latitude: marker.latitude, longitude: marker.longitude }}
      onPress={() =&gt; handleMarker(index)}
      ref={markerRef[index]}
  &gt;
  &lt;/Marker&gt;
  </code></pre>
  
  <p>Following is the Carousel that replaced <code>FlatList</code>:</p>
  
  <pre class="lang-js prettyprint-override"><code>&lt;Carousel
      data={items}
      renderItem={({ item }) =&gt; &lt;Item item={item}/&gt;}
      horizontal={true}
      ref={flatListRef}
      sliderWidth={width}
      sliderHeight={100}
      itemWidth={140}
      itemHeight={100}
  /&gt;
  </code></pre>
  
  <p>How do I achieve this this without <code>scrollToIndex</code>?</p>