Add option to import LibreTube exports esp. playlists

[ticklemyIP]

Checklist

• I made sure that there are no existing issues - open or closed - which I could contribute my information to.
• I have read the FAQ and my problem isn't listed.
• I'm aware that this is a request for NewPipe itself and that requests for adding a new service need to be made at NewPipeExtractor.
• I have taken the time to fill in all the required details. I understand that the feature request will be dismissed otherwise.
• This issue contains only one feature request.
• I have read and understood the contribution guidelines.

Feature description

I think it would be great to support a way to import playlists from other apps and services (including youtube), but mainly LibreTube.

Why do you want this feature?

Subscribtion import support currently is okay, but I think it could be expanded to saved playlist because that is the other main thing that is often needed to tranfer from one app to the other.

Additional information

No response