chore: update docs/immer with examples

docs/immer.md

@@ -1,6 +1,9 @@
 This doc describes `jotai/immer` bundle. 
+
 ## Install
+
 You have to install `immer` to access this bundle and its functions.
+
 ```
 npm install immer
 # or 
@@ -31,6 +34,12 @@ const Controls = () => {
 }
 ```
 
+### Examples
+
+Check examples with atomWithImmer:
+
+- https://codesandbox.io/s/jotai-immer-example-8zrqs
+
 ## withImmer
 
 `withImmer` takes an atom and returns a derived atom, same as `atomWithImmer` it has a different `writeFunction`.
@@ -56,8 +65,11 @@ const Controls = () => {
 ```
 
 ## useImmerAtom
+
 This hook takes an atom and replaces the atom's `writeFunction` with the new immer-like `writeFunction` like the previous helpers.
+
 ```jsx
+
 import { useAtom } from 'jotai'
 import { useImmerAtom } from 'jotai/immer'
 
@@ -78,5 +90,7 @@ const Controls = () => {
 ```
 
 It would be better if you don't use `withImmer` and `atomWithImmer` with `useImmerAtom` because they provide the immer-like `writeFunction` and we don't need to create a new one.
+
 ## Codesandbox
-A good example of this bundle in [codesandbox](https://codesandbox.io/s/immer-jotai-doc-ms9pv?file=/src/App.tsx).
+
+A good example of this bundle in [codesandbox](https://codesandbox.io/s/immer-jotai-doc-ms9pv?file=/src/App.tsx).