fix(docs): async guide (#1005)

* fix(docs): async guide

* minor fix

docs/guides/async.mdx

@@ -30,14 +30,17 @@ subscribe(store, () => {
 
 ## Suspend your React components
 
-Valtio supports React Suspense and will throw promises that you access within a components render function. This eliminates all the async back-and-forth. You can access your data directly while the parent is responsible for fallback state and error handling.
+Valtio is compatible with React 19 `use` hook. This eliminates all the async back-and-forth, you can access your data directly while the parent is responsible for fallback state and error handling.
 
 ```jsx
+import { use } from 'react' // React 19
+// import { use } from 'react18-use' // React 18
+
 const state = proxy({ post: fetch(url).then((res) => res.json()) })
 
 function Post() {
   const snap = useSnapshot(state)
-  return <div>{snap.post.title}</div>
+  return <div>{use(snap.post).title}</div>
 }
 
 function App() {
@@ -49,6 +52,8 @@ function App() {
 }
 ```
 
+It still suffers from "de-opt", which prevents `useTransition` to work well. To mitigate it, there is a third-party library [use-valtio](https://github.com/valtiojs/use-valtio).
+
 ## Codesandbox Pokemon fetch demo
 
 https://codesandbox.io/s/valtio-pokemon-fetch-x1lkbj?file=/src/App.tsx