docs: make sidebar config a bit more organized

docs/.vitepress/config.js

@@ -20,7 +20,15 @@ module.exports = {
     ],
 
     sidebar: {
-      '/guide/': [
+      '/': getGuideSidebar(),
+      '/guide/': getGuideSidebar(),
+      '/config/': getConfigSidebar()
+    }
+  }
+}
+
+function getGuideSidebar() {
+  return [
     {
       text: 'Introduction',
       children: [
@@ -31,8 +39,9 @@ module.exports = {
         { text: 'Deploying', link: '/guide/deploy' }
       ]
     }
-      ],
-      '/config/': [{ text: 'Config Reference', link: '/config/' }]
-    }
-  }
+  ]
+}
+
+function getConfigSidebar() {
+  return [{ text: 'Config Reference', link: '/config/' }]
 }