Apply transform method to <video poster>

[zachleat]

Vote from @eaton https://phire.place/@eaton/112933092208311738

[eaton]

To offer a little more background, I'm migrating a huge pile of content with "embed codes" for images and videos. eleventy-img has radically simplified the process of managing the the images, but keeping our video thumbnail handling consistent with static image handling has required a whole parallel set of tweaks and transforms.

This would make that orders of magnitude simpler; big thumbs up from me.

[ryangittings]

+1!

[zachleat]

Duplicate of #215 (though this one is more specific)—let’s regroup over there!