feat[Menu]: menu icon support el-icon

src/router/index.js

@@ -19,7 +19,7 @@ import Layout from '@/layout'
  * meta : {
     roles: ['admin','editor']    control the page roles (you can set multiple roles)
     title: 'title'               the name show in sidebar and breadcrumb (recommend set)
-    icon: 'svg-name'             the icon show in the sidebar
+    icon: 'svg-name'/'el-icon-x' the icon show in the sidebar
     breadcrumb: false            if set false, the item will hidden in breadcrumb(default is true)
     activeMenu: '/example/list'  if set path, the sidebar will highlight the path you set
   }
@@ -60,7 +60,7 @@ export const constantRoutes = [
     component: Layout,
     redirect: '/example/table',
     name: 'Example',
-    meta: { title: 'Example', icon: 'example' },
+    meta: { title: 'Example', icon: 'el-icon-s-help' },
     children: [
       {
         path: 'table',