Add Vue.js Fundamentals course (#4048)

Add Vue.js Fundamentals course from VueSchool

free-courses-en.md

@@ -310,6 +310,7 @@
 
 * [Intro to Vue 2](https://www.vuemastery.com/courses/intro-to-vue-js/vue-instance)
 * [Intro to Vue 3](https://www.vuemastery.com/courses/intro-to-vue-3/intro-to-vue3)
+* [Vue.js Fundamentals](https://vueschool.io/courses/vuejs-fundamentals)
 
 
 ### Kubernetes