docs: add an example for setting the state outside event (#302)

readme.md

@@ -363,6 +363,34 @@ import { redux } from 'zustand/middleware'
 const useStore = create(redux(reducer, initialState))
 ```
 
+## Calling actions outside a React event handler
+
+Because React handles `setState` synchronously if it's called outside an event handler. Updating the state outside an event handler will force react to update the components synchronously, therefore adding the risk of encountering the zombie-child effect.
+In order to fix this, the action needs to be wrapped in `unstable_batchedUpdates`
+
+```jsx
+import create from 'zustand'
+import { unstable_batchedUpdates } from 'react-dom';
+
+export const useStore = create(persist(
+  (set) => ({
+    fishes: 0,
+    addAFish: () => set({ fish: get().fish + 1 })
+  }),
+))
+
+const addAFish = useStore((state) => state.addAFish)
+
+async function onClickHandler() {
+  await asyncFunc()
+  unstable_batchedUpdates(() => {
+    addAFish()
+  })
+}
+```
+
+More details: https://github.com/pmndrs/zustand/issues/302
+
 ## Redux devtools
 
 ```jsx