Get expected size of video asset during SSG to create placeholder

[sjstark]

Just a thought at this point and haven't really thought about where to do it, but figured since we're more often than not generating our sites, we could get the expected aspect ratio of a video during generation to create a placeholder at the correct size to prevent sites jumping when the asset loads...

Further more, if we're really feeling it, I bet we could grab the first frame of the video for a placeholder image... but that may be more effort than is worth.

[weotch]

Ooooh, caching the aspects to disk during SSG is s cool idea. I think we could even use Nuxt's fetch() hook for that ... and this package makes it look pretty easy: https://www.npmjs.com/package/get-video-dimensions. Cool idea!