Add explicit Title and Artist types

karaokatalog/Song.py

@@ -6,6 +6,9 @@ import filecmp
 
 from dataclasses import dataclass
 
+type Title = str
+type Artist = str
+
 
 @dataclass(frozen=True)
 class Song:
@@ -15,8 +18,8 @@ class Song:
     See https://usdx.eu/format/ for the specification.
     """
 
-    title: str
-    artist: str
+    title: Title
+    artist: Artist
     audio: Path | None
     video: Path | None
     cover: Path | None