Add basic spectator screen

osu.Game.Tests/Visual/Gameplay/TestSceneSpectator.cs

@@ -0,0 +1,20 @@
+// 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 NUnit.Framework;
+using osu.Game.Screens.Play;
+using osu.Game.Users;
+
+namespace osu.Game.Tests.Visual.Gameplay
+{
+    public class TestSceneSpectator : ScreenTestScene
+    {
+        private readonly User user = new User { Id = 1234, Username = "Test user" };
+
+        [Test]
+        public void TestSpectating()
+        {
+            AddStep("load screen", () => LoadScreen(new Spectator(user)));
+        }
+    }
+}

osu.Game/Screens/Play/Spectator.cs

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+// 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 JetBrains.Annotations;
+using osu.Framework.Allocation;
+using osu.Framework.Graphics;
+using osu.Game.Graphics.Sprites;
+using osu.Game.Users;
+
+namespace osu.Game.Screens.Play
+{
+    public class Spectator : OsuScreen
+    {
+        private readonly User targetUser;
+
+        public Spectator([NotNull] User targetUser)
+        {
+            this.targetUser = targetUser ?? throw new ArgumentNullException(nameof(targetUser));
+        }
+
+        [BackgroundDependencyLoader]
+        private void load()
+        {
+            InternalChildren = new Drawable[]
+            {
+                new OsuSpriteText
+                {
+                    Text = $"Watching {targetUser}",
+                    Anchor = Anchor.Centre,
+                    Origin = Anchor.Centre,
+                },
+            };
+        }
+    }
+}