Please add missing elements from Facebook SDK

Hi,

I´m adding custom video as Cover, and managed to do so, but only when I modify the plugin core class.

In class-instant-articles-post.php :

Missing:

use Facebook\InstantArticles\Elements\Video;

In function to_instant_article() a simple check for Video could be added like this:

$cover = $this->get_the_featured_image();
		if ( $cover['src'] ) {
			// Check if cover type is video / image
			if ( $cover['type'] == 'video' ) {
				$image = Video::create()->withURL( $cover['src'] );
			} else {
				$image = Image::create()->withURL( $cover['src'] );
			}
			if ( isset( $cover['caption'] ) && strlen( $cover['caption'] ) > 0 ) {
				$image->withCaption(
				    Caption::create()->withTitle( $cover['caption'] )
				);
			}

			$header->withCover( $image );
		}

Then its possible to modify the preferred output of video or image with a filter to hook into instant_articles_featured_image()

https://wordpress.org/plugins/fb-instant-articles/