Add a Youtube playlist content inside a user playlist

[Krusty27]

Checklist

• I checked, but didn't find any duplicates (open OR closed) of this issue in the repo.
• I have read the contribution guidelines given at https://github.com/TeamNewPipe/NewPipe/blob/HEAD/.github/CONTRIBUTING.md.
• This issue contains only one feature request. I will open one issue for every feature I want to request.

What feature do you want?

Ability to add a playlist (or all of its content) from Youtube (Music) search results inside another custom playlist.

Why do you want this feature?

As of now, a user can add an already made playlist only generally in the bookmarked playlist, but I would like to be able to add all of the playlist music inside another playlist. For example, if I want to create a playlist which groups all of an artist's songs going album by album in the Youtube Music search results.

Thanks for your important work!