docs(readme): Adding extract-css-chunks to readme

Adding it to the documentation as a alternative / extended version of mini-css-extract. 
Extract css chunks offers hot module reloading while in development, allowing for good performance on the client and build. 
As you guys will know, mini-css is fast, this brings the benefits of it to development without losing the ability to hot reload.

Author: ScriptedAlchemy

README.md

@@ -658,7 +658,9 @@ module.exports = {
 ### Extract
 
 For production builds it's recommended to extract the CSS from your bundle being able to use parallel loading of CSS/JS resources later on.
-This can be achieved by using the [mini-css-extract-plugin](https://github.com/webpack-contrib/mini-css-extract-plugin) to extract the CSS when running in production mode.
+This can be achieved by using the [mini-css-extract-plugin](https://github.com/webpack-contrib/mini-css-extract-plugin) to extract the CSS when running in production mode. 
+
+As an alternative, if seeking better development performance and css outputs that mimic production. [extract-css-chunks-webpack-plugin](https://github.com/faceyspacey/extract-css-chunks-webpack-plugin) offers a hot module reload friendly, extended version of mini-css-extract-plugin. HMR real CSS files in dev, works like mini-css in non-dev
 
 ## Contributing