Search: Add Filter "Playlist"

[Russe]

Feature Description

Currently you can not search for tracks which are in specific playlists.
There is no filter for "playlist"
https://manual.mixxx.org/2.4/en/chapters/library#finding-tracks-search

I would like to search for tracks which are in specific playlists or tracks which are in no playlist at all.
Here are some examples:
playlist:"best songs of my life"
playlist:""

Is there any chance to get this into Mixxx?

[daschuer]

We have already the same for crates. Adding it for playlist should be no issue.

mixxx/src/library/searchqueryparser.cpp

Line 84 in 6efbf8c

<< "crate"

We just need a contributor to do that.