cozy: add gst-plugin-bad

This adds support for: ISO Media, Apple iTunes ALAC/AAC-LC (.M4A) Audio

pkgs/applications/audio/cozy-audiobooks/default.nix

···
     gst-plugins-good
     gst-plugins-ugly
     gst-plugins-base
+    gst-plugins-bad
   ]);
 
   propagatedBuildInputs = with python3Packages; [