Add album or curated playlist to a playlist

[SimonSimCity]

The api already has an endpoint to add an album or playlist to a playlist.

For the design: Add a "3 dot" button to album and curated playlist, next to the share button (3 dot button is already used for private playlists to offer a menu to edit or delete). When clicking that new button a menu with 1 entry "Add to playlist" appears. That button opens the playlist selection. (Same as for single track)

[kkuepper]

@julo-web-dev Removed Assignees since there's no PR after 2 months.

[kkuepper]

I implemented adding a song to a playlist in #281. I don't actually see in the design how you could add an album to a playlist.