Add support for moving object with transform gizmo when mouse moves outside the viewport during usage

Source/Editor/Viewport/EditorGizmoViewport.cs

@@ -73,6 +73,9 @@ namespace FlaxEditor.Viewport
         /// <inheritdoc />
         public Undo Undo { get; }
 
+        /// <inheritdoc />
+        protected override bool IsControllingMouse => Gizmos.Active?.IsControllingMouse ?? false;
+
         /// <inheritdoc />
         protected override void AddUpdateCallbacks(RootControl root)
         {