fix #245, Add FAQs page

Author: znck

docs/.vuepress/config.js

@@ -25,6 +25,10 @@ module.exports = {
           {
             text: 'Migrating from v2',
             link: '/migrating'
+          },
+          {
+            text: 'FAQs',
+            link: '/faqs'
           }
         ],
         sidebar: [

docs/faqs.md

@@ -0,0 +1,7 @@
+# Frequently Asked Questions
+
+- **Why does `__file` use absolute path?**
+  The `__file` variable is used by devtools to provide "open in editor" feature. However, in production mode only filename is used. See issue [#258](https://github.com/vuejs/rollup-plugin-vue/issues/258) to enable production mode.
+
+- **Cannot find module `vue-template-compiler`?**
+  `vue-template-compiler` has a constraint that it should be exact same version as `vue` that is why it is included as peer dependency. Make sure you install `vue-template-compiler` and `vue` in your project.