fix(demo-free-layout): group node cannot be dragged in the mouse mode (#864)

apps/demo-free-layout/src/components/group/components/node-render.tsx

@@ -55,6 +55,7 @@ export const GroupNodeRender = () => {
           <GroupHeader
             onDrag={(e) => {
               startDrag(e as MouseEvent);
+              e.stopPropagation();
             }}
             onFocus={onFocus}
             onBlur={onBlur}