fix: changed sidebar structure

Author: ntepluhina

src/.vuepress/config.js

@@ -26,12 +26,21 @@ module.exports = {
     sidebarDepth: 2,
     sidebar: {
       '/guide/': [
-        'installation',
-        'introduction',
-        'instance',
-        'template-syntax',
-        'computed',
-        'class-and-style'
+        {
+          title: 'Essentials',
+          collapsable: true,
+          children: [
+            'installation',
+            'introduction',
+            'instance',
+            'template-syntax',
+            // 'computed',
+            // 'class-and-style',
+            // 'conditional',
+            // 'list'
+            // 'events'
+          ]
+        }
       ]
     }
   },