Added workaround for + on Mac as well.

Author: Oliver-Loeffler

app/src/main/java/com/oracle/javafx/scenebuilder/app/menubar/MenuBarController.java

@@ -1342,6 +1342,11 @@ public void handleAdditionalZoomAccelerators(KeyEvent event) {
             return;
         }
 
+        if (EditorPlatform.IS_MAC && "+".equals(event.getText())) {
+            runActionController(zoomInController, event);
+            return;
+        }
+
         if (event.isShiftDown()) {
             handleArrowKeysForZoom(event);
         } else {