add YouTube playlist support via command

[irgendwr]

Add YouTube playlist support via command, for example: !yt <playlist url> or !ytplaylist <playlist url>

Downsides:

• the user would need to provide API-key, or
• playlists could also be implemented with youtube-dl but flyth would need to add scripting methods for that

[mxschmitt]

Does the Youtube WebInterface not work?

[irgendwr]

Does the Youtube WebInterface not work?

dunno, probably works but I want to have this in the default commands

[rickdgray]

I would love for this to be added