Update README.md

Author: typicode

README.md

@@ -297,6 +297,7 @@ If you need to add authentication, validation, or __any behavior__, you can use
 __Simple example__
 
 ```js
+// server.js
 var jsonServer = require('json-server')
 var server = jsonServer.create()
 var router = jsonServer.router('db.json')
@@ -309,6 +310,10 @@ server.listen(3000, function () {
 })
 ```
 
+```sh
+$ node server.js
+```
+
 For an in-memory database, you can pass an object to `jsonServer.router()`.
 Please note also that `jsonServer.router()` can be used in existing Express projects.