Updated link to Mix

Author: royklutman

README.md

@@ -9,7 +9,7 @@ and minifying assets. Encore gives you professional asset system
 that's a *delight* to use.
 
 Encore is inspired by [Webpacker](https://github.com/rails/webpacker) and
-[Mix](https://laravel.com/docs/5.4/mix), but stays in the spirit of
+[Mix](https://laravel.com/docs/5.6/mix), but stays in the spirit of
 Webpack: using its features, concepts and naming conventions for a familiar
 feel. It aims to solve the most common Webpack use cases.