Add EditorPlugin.DeinitializeEditor to properly cleanup Editor extensions on exit

Source/Editor/Editor.cs

@@ -569,6 +569,10 @@ namespace FlaxEditor
         {
             Log("Editor exit");
 
+            // Deinitialize Editor Plugins
+            foreach (var plugin in PluginManager.EditorPlugins)
+                ((EditorPlugin)plugin).DeinitializeEditor();
+
             // Start exit
             StateMachine.GoToState<ClosingState>();
 

Source/Editor/Plugins/EditorPlugin.cs

@@ -52,5 +52,12 @@ namespace FlaxEditor
         public virtual void InitializeEditor()
         {
         }
+
+        /// <summary>
+        /// Cleanup method called when this plugin is initialized and Editor is disposing (before plugin disposing). Use this method to remove any custom editor functionalities created within InitializeEditor.
+        /// </summary>
+        public virtual void DeinitializeEditor()
+        {
+        }
     }
 }