Feature/english (#381)

* perf[navbar]: set langSelect to component && refine errorLog component

* feat[login]:add 18n to login form

* fix[pagination]: fixed when selected page-sizes

* perf[i18n]:dashboard document svg permission

* perf[charts]: perf effect

* perf[i18n]:excel && zip

* perf[i18n]: table && errorLog && theme

* perf[i18n]: components

* perf[i18n]: direct use $t

* perf[i18n]: complex-table

* update README.md

* update README.md 📘

* perf[i18n]: refine code comments

src/router/index.js

@@ -9,6 +9,10 @@ Vue.use(Router)
 /* Layout */
 import Layout from '../views/layout/Layout'
 
+/** note: submenu only apppear when children.length>=1
+*   detail see  https://panjiachen.github.io/vue-element-admin-site/#/router-and-nav?id=sidebar
+**/
+
 /**
 * hidden: true                   if `hidden:true` will not show in the sidebar(default is false)
 * redirect: noredirect           if `redirect:noredirect` will no redirct in the breadcrumb