fix: copilot not working (#3425)

plugins/hello-world/src/index.ts

@@ -20,6 +20,14 @@ export const entry = (context: PluginContext) => {
     };
   });
 
+  context.register('formatBar', div => {
+    const root = createRoot(div);
+    root.render(createElement(HeaderItem));
+    return () => {
+      root.unmount();
+    };
+  });
+
   return () => {
     console.log('unregister');
   };