UI: Option to automatically Hide UI when game launches (#462)

Quality of life feature
Similar in function to the "Start Games in Fullscreen" toggle
For users who want to run games in windowed/non-fullscreen mode with
menu UI hidden, this eliminates the need to always click "Hide UI"

src/Ryujinx/Utilities/Configuration/ConfigurationState.Model.cs

@@ -152,6 +152,11 @@ namespace Ryujinx.Ava.Utilities.Configuration
             /// </summary>
             public ReactiveObject<bool> StartFullscreen { get; private set; }
 
+            /// <summary>
+            /// Start games with UI hidden
+            /// </summary>
+            public ReactiveObject<bool> StartNoUI { get; private set; }
+
             /// <summary>
             /// Hide / Show Console Window
             /// </summary>
@@ -192,6 +197,7 @@ namespace Ryujinx.Ava.Utilities.Configuration
                 WindowStartup = new WindowStartupSettings();
                 BaseStyle = new ReactiveObject<string>();
                 StartFullscreen = new ReactiveObject<bool>();
+                StartNoUI = new ReactiveObject<bool>();
                 GameListViewMode = new ReactiveObject<int>();
                 ShowNames = new ReactiveObject<bool>();
                 GridSize = new ReactiveObject<int>();