Use media:group/media:description if it exists

Use media:group/media:description if it exists

Some feeds (typically rss feeds from invidious channels) have the
following structure for entries:

<item>
	[...]
	<content></content>
	<description>A one line title</description>
	<media:group>
		[...]
		<media:description>An actual text
that serves
as a description</media:description>
	</media:group>
</item>

If it's there, and again longer than the other fields, use it