refactor(v2): change the label for docs introduction (#2716)

* change the label for docs introduction

* change file id

* refactor(v2): change name

website/docs/docs.md

@@ -1,5 +1,5 @@
 ---
-id: docs
+id: docs-introduction
 title: Docs Introduction
 sidebar_label: Introduction
 ---

website/sidebars.js

@@ -14,7 +14,7 @@ module.exports = {
       'styling-layout',
       'static-assets',
       {
-        Docs: ['docs', 'markdown-features', 'versioning'],
+        Docs: ['docs-introduction', 'markdown-features', 'versioning'],
       },
       'blog',
       'search',