Add skin components and interfaces

osu.Game/Skinning/HUDSkinComponent.cs

@@ -0,0 +1,22 @@
+// 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.
+
+using System.Linq;
+
+namespace osu.Game.Skinning
+{
+    public class HUDSkinComponent : ISkinComponent
+    {
+        public readonly HUDSkinComponents Component;
+
+        public HUDSkinComponent(HUDSkinComponents component)
+        {
+            Component = component;
+        }
+
+        protected virtual string ComponentName => Component.ToString();
+
+        public string LookupName =>
+            string.Join("/", new[] { "HUD", ComponentName }.Where(s => !string.IsNullOrEmpty(s)));
+    }
+}