Move metrics to beatmap set

osu.Game/Beatmaps/BeatmapSetMetrics.cs

@@ -0,0 +1,17 @@
+// 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;
+using Newtonsoft.Json;
+
+namespace osu.Game.Beatmaps
+{
+    public class BeatmapSetMetrics
+    {
+        /// <summary>
+        /// Total vote counts of user ratings on a scale of 0..10 where 0 is unused (probably will be fixed at API?).
+        /// </summary>
+        [JsonProperty("ratings")]
+        public int[] Ratings { get; set; } = Array.Empty<int>();
+    }
+}