fix: enable strict mode (#3321)

apps/core/src/index.tsx

@@ -1,4 +1,5 @@
 import { assertExists } from '@blocksuite/global/utils';
+import { StrictMode } from 'react';
 import { createRoot } from 'react-dom/client';
 
 async function main() {
@@ -7,7 +8,11 @@ async function main() {
   const root = document.getElementById('app');
   assertExists(root);
 
-  createRoot(root).render(<App />);
+  createRoot(root).render(
+    <StrictMode>
+      <App />
+    </StrictMode>
+  );
 }
 
 await main();