Add HasQuit gameplay state

osu.Game/Screens/Play/GameplayState.cs

@@ -49,6 +49,11 @@ namespace osu.Game.Screens.Play
         /// </summary>
         public bool HasFailed { get; set; }
 
+        /// <summary>
+        /// Whether the user quit gameplay without either having either passed or failed.
+        /// </summary>
+        public bool HasQuit { get; set; }
+
         /// <summary>
         /// A bindable tracking the last judgement result applied to any hit object.
         /// </summary>