By the default mpv tries opening URLs with ffmpeg first, and users who
don't configure try_ytdl_first get a slower startup for youtube URLs, on
top of yt-dlp already being slow.
Fix this by adding a script-opt of URL pattern to try with ytdl first.
Youtube and twitch are included by default.
Compared to the alternative of trying ytdl first by default and
excluding URLs with a media extension, this only works for the sites
explicitly included in the new option's value, but doesn't have false
positives on media URLs without an extension.
Guido Cella