[Docs]: incorrect documentation for the "inPlaylist" operator for Smart Playlists

### I confirm that: - [x] This issue is about the **documentation website**, NOT about the Navidrome server ### Page URL or path https://www.navidrome.org/docs/usage/features/smart-playlists/#operators ### What's wrong Currently, the docs state that it accepts "Another playlist’s ID" as an argument, while it actually works more as the `is` operator, where you have to give it a condition based on a field (`id` in case you actually want to filter an id). Here's how I tried to use it initially. ```jsonc { // ... "all": [ { "inPlaylist": "dVX0hgcj4JJFjTs66xpEqI" } ], // ... } ``` Here's the actual working example ```jsonc { // ... "all": [ { "inPlaylist": { "id": "dVX0hgcj4JJFjTs66xpEqI" } } ], // ... } ``` I believe that it's the same case with the `notInPlaylist` operator. I think that in the section, which shows how to get a playlists ID, it'd be very useful to also give a working `nsp` example using the playlist's ID which should help minimize any confusion. Thanks for giving us this great software! ### Suggested fix Update the arguments for `inPlaylist` and `notInPlaylist` to say "String, Number, Boolean" instead of "Another playlist’s ID (see below)" and add at least one usage example.