Update extending.md

Author: yanxyz

source/guide/extending.md

@@ -77,4 +77,4 @@ Vue.use(require('my-plugin'), {
 - [vue-element](https://github.com/vuejs/vue-element): Register Custom Elements with Vue.js.
 - [List of User Contributed Tools](https://github.com/yyx990803/vue/wiki/User-Contributed-Components-&-Tools)
 
-Next: [Common FAQs](/guide/faq.html).
+Next: [Tips & Best Practices](/guide/best-practices.html).