feat: add configurable artist separator

internal/config/config.go

@@ -142,6 +142,7 @@ type ArtworkConfig struct {
 type MetadataConfig struct {
 	SetPlaylistToAlbum     bool     `toml:"set_playlist_to_album"`
 	RenumberPlaylistTracks bool     `toml:"renumber_playlist_tracks"`
+	ArtistSeparator        string   `toml:"artist_separator"`
 	Exclude                []string `toml:"exclude"`
 }
 
@@ -297,6 +298,7 @@ func DefaultConfigData() ConfigData {
 		Metadata: MetadataConfig{
 			SetPlaylistToAlbum:     true,
 			RenumberPlaylistTracks: true,
+			ArtistSeparator:        "; ",
 			Exclude:                []string{},
 		},
 		Filepaths: FilepathsConfig{