Add legacy font enum and extensions

osu.Game/Skinning/LegacyFont.cs

@@ -0,0 +1,15 @@
+// Copyright (c) ppy Pty Ltd <contact@ppy.sh>. Licensed under the MIT Licence.
+// See the LICENCE file in the repository root for full licence text.
+
+namespace osu.Game.Skinning
+{
+    /// <summary>
+    /// The type of legacy font to use for <see cref="LegacySpriteText"/>s.
+    /// </summary>
+    public enum LegacyFont
+    {
+        Score,
+        Combo,
+        HitCircle,
+    }
+}