feat: init @affine/docs (#2849)

apps/docs/src/index.tsx

@@ -0,0 +1,14 @@
+import './index.css';
+
+import { StrictMode } from 'react';
+import { createRoot } from 'react-dom/client';
+import { serve } from 'waku/client';
+
+const App = serve('App');
+const rootElement = (
+  <StrictMode>
+    <App />
+  </StrictMode>
+);
+
+createRoot(document.getElementById('root') as HTMLElement).render(rootElement);