Handle video conversion correct

Current video elements are not converted

```
<figure class="wp-block-video"><video controls src="https://cdn.shopify.com/videos/c/vp/86f20b733de249c69f3f21625a0db57c/86f20b733de249c69f3f21625a0db57c.HD-1080p-7.2Mbps-17207217.mp4"></video></figure>
```