Update add video ot playlist prompt to show presence count when adding one video

[PikachuEXE]

Pull Request Type

• [ ] Bugfix
• [x] Feature Implementation
• [ ] Documentation
• [ ] Other

Related issue

https://github.com/PikachuEXE/FreeTube/issues/55

Description

When adding one video, display no. of times the video is added in playlists If not added nothing extra would be displayed

Screenshots

Testing

• Create Playlist (A) & (B) (if needed)
• Add a video to A once, B twice (or more)
• Try to add the same video again to see what's displayed

Desktop

• OS:
• OS Version:
• FreeTube version:

Additional context

I got text for adding 2+ videos ready but probably easier reviewing this first