set youtube playback speed on a per-feed basis

[guest20]

[x] I have read this document: https://miniflux.app/opinionated.html#feature-request

As one who watches youtube videos I want to be able to set playback speed at channel level, so I can enjoy videos from some more laid-back folks at 2x playback speed while slowing down the playback from some of the more enthusiastic youtubers.

I think this might be a Rewrite rule?