[PATCH] emms-info-ytdl

Hello,

Few years ago Yuchen Pei started to develop emms-info-ytdl (branch
info-ytdl), which provides info for links like:
https://www.youtube.com/watch?v=.....

I do not know why these changes where not accepted in master.
Perhaps it is because ytdl is called synchronously, and therefore
emms-info-ytdl freezes Emacs.

For a few years i am using without any problem the version, which works
asynchronously.

Please find attached the asynchronous version of emms-info-ytdl.

I am not programmer, so maybe there are some style things.
With some guidance, i am ready to correct them.
I hope it can be added in emms.