doc: update express app example (#6718)

Author: shivarm

Readme.md

@@ -40,7 +40,9 @@ app.get('/', (req, res) => {
   res.send('Hello World')
 })
 
-app.listen(3000)
+app.listen(3000, () => {
+  console.log('Server is running on http://localhost:3000')
+})
 ```
 
 ## Installation