Comprehensive benchmark of image presets

Testing Webp support on youtube showed that WebpHigh doesn't produce high quality thumbnail.
As these image presets are going to be used everywhere, it's important that, now that the rest works and before we actually roll it out everywhere, we run a benchmark of all presets.

What I envision is a table of a small (10?) list of images used in our scrapers for each format, with, side-by-side: the original, and the three presets version.

That should help us validate or revise the presets variable. It would also serve as a reference in the future, when we have to choose what preset to use for a scraper.

http://tmp.kiwix.org/youtube/report.html can serve as an inspiration