feat: add configurable artist separator

config.toml.example

@@ -155,6 +155,8 @@ saved_max_width = -1
 set_playlist_to_album = true
 # Use playlist position as tracknumber for playlist items
 renumber_playlist_tracks = true
+# Separator used when a provider exposes multiple artists as separate values
+artist_separator = "; "
 # Metadata fields to exclude from tagging
 exclude = []