Add xmldoc

osu.Game/Screens/Play/Player.cs

@@ -312,6 +312,10 @@ namespace osu.Game.Screens.Play
                 this.Exit();
         }
 
+        /// <summary>
+        /// Restart gameplay via a parent <see cref="PlayerLoader"/>.
+        /// <remarks>This can be called from a child screen in order to trigger the restart process.</remarks>
+        /// </summary>
         public void Restart()
         {
             sampleRestart?.Play();