Implement MappingSubscribersButton component

osu.Game/Overlays/Profile/Header/Components/FriendsButton.cs

@@ -0,0 +1,26 @@
+// 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.Allocation;
+using osu.Framework.Bindables;
+using osu.Framework.Graphics.Sprites;
+using osu.Game.Users;
+
+namespace osu.Game.Overlays.Profile.Header.Components
+{
+    public class FriendsButton : ProfileHeaderStatisticsButton
+    {
+        public readonly Bindable<User> User = new Bindable<User>();
+
+        public override string TooltipText => "followers";
+
+        protected override IconUsage CreateIcon() => FontAwesome.Solid.User;
+
+        [BackgroundDependencyLoader]
+        private void load()
+        {
+            // todo: when friending/unfriending is implemented, the APIAccess.Friends list should be updated accordingly.
+            User.BindValueChanged(user => SetValue(user.NewValue?.FollowerCount ?? 0), true);
+        }
+    }
+}