title: React Native FlatList jumps to the top when adding new items
body: <p>I'm trying to add an Infinite Scroll feature to a FlatList:</p>
  
  <pre><code>&lt;FlatList
     data={pickupsGroups}
     renderItem={({item , index}: {item: PickupGroup, index: number}) =&gt; {
                      return &lt;PickingCard group={item} onPress={onPressPickup}/&gt;
     }}
     onRefresh={onRefresh}
     keyExtractor={item =&gt; `${item?.title}-${item?.totalSku}`}
     refreshing={refreshing}
     onEndReached={() =&gt; {
       setPage(page + 1)
     }}
     onEndReachedThreshold={0.1}
  /&gt;
  </code></pre>
  
  <p>when the <code>page</code> changes, I run a GraphQL query:</p>
  
  <pre><code>    const {loading} = useQuery(MY_GROUPS, {
          variables: {limit: 10, page},
          fetchPolicy: "network-only",
          onCompleted: data =&gt; {
              setPickupsGroups(pickupsGroups.concat(data.myPickupGroups.pickupGroups))
          }
      })
  </code></pre>
  
  <p>But every time I add new items to <code>pickupGroups</code>, the FlatList scrolls back to the top</p>