configure to allow updating artist separators

+ remove ampersand from default
+ misc

app/utils/parsers.py

@@ -8,7 +8,8 @@ def split_artists(src: str):
     """
     Splits a string of artists into a list of artists.
     """
-    separators = get_flag(ParserFlags.ARTIST_SEPARATORS)
+    separators: set = get_flag(ParserFlags.ARTIST_SEPARATORS)
+    separators = separators.union({","})
 
     for sep in separators:
         src = src.replace(sep, "߸")