Implement video quality selection

## Example:
```html
<video-nd class="youtube" src="/video/demo-HD.ndjson" controls loop autoplay fps="30" autosize>
       <source src="/video/demo-QVGA.ndjson" width="320">
       <source src="/video/demo-4K.ndjson" width="3840" height="2160">
</video-nd>
```

* Display a selector to switch between quality images. 