Dynamic / lazy approach to load pages

# Feature Request

## Why it is needed

Performance way to load a LOT of pages dynamically to create a truly dynamic swiper.

## Possible implementation / Code sample

Right now I can do something like:

```js
const [position, setPosition] = useState(0);

const onPageSelected = e => {
setPosition(e.nativeEvent.position);
};

const min = 0;
const max = position + numberOfPages;

const items = data.slice(min, max).map((item, index) => (
// If they are are not inside the range, we render null to get a better performance

{index < position + numberOfPages && index > position - numberOfPages ? (

) : null}

));

...
>
{items}

```

**Contraints**: List keeps growing while you swipe.

A better way instead of rendering `null` would be to slice from the beginning too:

```js
const min = position - numberOfPages;
const max = position + numberOfPages;
```

However, this approach has a problem. Consider the scenario:

* Pages: `1 2 3 4` and position = 2 (selected element is 3).

We slice from the beginning and we render:

* Pages `2 3 4 5` but still position = 2 (selected element will be 4). <-- The problem is that if we change the children in this way, we need to adapt the position (here the position should be 1 for selected element to be still 3).

---

Another approach would be doing this by default natively: https://github.com/react-native-community/react-native-viewpager/issues/83.

Beginne mit den beiden Beispielen für Child Windows im Issue und der verlinkten Diskussion react-native-community/react-native-viewpager#83, um die nativen Einschränkungen zu verstehen. Erledigt ist die Aufgabe, wenn ein dokumentierter, dynamischer Ansatz bereitgestellt wird, der viele Seiten verzögert laden kann und dabei die ausgewählte Seite beibehält, während die Liste wächst.

Vom Indexierungsmodell aus dem Issue-Text verfasst.