Add localisation support to overlay header title/description

osu.Game/Localisation/NowPlayingStrings.cs

@@ -0,0 +1,24 @@
+// 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 osu.Framework.Localisation;
+
+namespace osu.Game.Localisation
+{
+    public static class NowPlayingStrings
+    {
+        private const string prefix = "osu.Game.Localisation.NowPlaying";
+
+        /// <summary>
+        /// "now playing"
+        /// </summary>
+        public static LocalisableString HeaderTitle => new TranslatableString(getKey("header_title"), "now playing");
+
+        /// <summary>
+        /// "manage the currently playing track"
+        /// </summary>
+        public static LocalisableString HeaderDescription => new TranslatableString(getKey("header_description"), "manage the currently playing track");
+
+        private static string getKey(string key) => $"{prefix}:{key}";
+    }
+}