update readme

Author: Plortinus

README.md

@@ -65,6 +65,7 @@ node server.js
 ├── .eslintrc.js    # eslint config
 ├── server.js       # port 2333
 ├── webpack.config.js # webpack config
+├── postcss.config.js # postcss config
 ├── node_modules    # dependencies
 └── package.json    # package info
 ```