Add the option to download all videos of a Playlist

[Outlet2048]

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?

Add an option to download all videos in a Playlist at once

Why do you want this feature?

I got Playlist with videos that I want to save but I definitely don't want to download every single video on its own.
A play all button already exists, so a download all button would be a nice addition

This also improves the user experience for people who keep music in playlists using newpipe

[SameenAhnaf]

Duplicate of #5482 .