Add duplicate warning when adding video to playlist which has already been added

[Mati20187]

Checklist

• I made sure that there are no existing issues - open or closed - which I could contribute my information to.
• 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

It would be nice to have a pop-up saying something like:
This video has already been added to the playlist. Do you want to add it anyway?
And have options:
Add and Cancel

Why do you want this feature?

I often end up with duplicates in my playlists: I add a song to "Music" playlist, stumble upon the same song in watch suggestions a month later and add it again.

Additional information

No response

[SameenAhnaf]

Duplicate of #4186