Add an update playlist method

[Bob-vdV]

There are methods for creating and deleting playlists, but currently there is no way to update an existing playlist.
The official documentation for updating playlists is here: https://developers.soundcloud.com/docs/api/explorer/open-api#/playlists/put_playlists__playlist_id_
Is it possible to add this without an API key?

[Bob-vdV]

I've written some draft functions that do appear to update the playlist, but also throw a dacite.MissingValueError for the created_at field. Any idea on how to fix this? It seems like created_at is not set anywhere else.

Update functions:
in ./soundcloud.py:

    def update_playlist(
        self,
        playlist_id: int,
        sharing: Literal["private", "public"],
        title: str,
        tracks: List[int],
    ) -> Optional[BasicAlbumPlaylist]:
        """
        Update a playlist
        """
        body = {"playlist": {"sharing": sharing, "title": title, "tracks": tracks}}
        return PutPlaylistRequest(self, playlist_id=playlist_id, body=body)

In requests.py:

PutPlaylistRequest = Request[BasicAlbumPlaylist](
    "/playlists/{playlist_id}", BasicAlbumPlaylist, method="PUT"
)