Add Free Book & Course of Vue.js (#6398)

* Add Free Book and Course of Vue.js

* Remove Duplicate & Giving Lecturer Credits

* Update free-courses-en.md

courses/free-courses-en.md

@@ -594,6 +594,7 @@
 
 #### Vue.js
 
+* [Full Stack Vue.js, Express & MongoDB](https://www.youtube.com/playlist?list=PLillGF-RfqbYSx-Ab1xWVanGKtowTsnNm) - Traversy Media (Youtube)
 * [Get Started with Nuxt](https://explorers.netlify.com/learn/get-started-with-nuxt) - Debbie O'Brien (Netlify)
 * [Internationalization with vue-i18n](https://vueschool.io/courses/internationalization-with-vue-i18n)
 * [Intro to Vue 2](https://www.vuemastery.com/courses/intro-to-vue-js/vue-instance)