feat(component): helper function observeResize to observe size change via global ResizeObserver (#7241)

```ts
import { observeResize } from "@affine/component";

useEffect(() => {
  const dispose = observeResize(element entry => {
    console.log(entry.contentRect);
  });

  return () => dispose();
}, []);
```

packages/frontend/component/src/utils/index.ts

@@ -0,0 +1 @@
+export * from './observe-resize';