refactor: new add extra-page

部分文件移动至新的文件夹，项目结构更简洁美观

docs/extra-page/README.md

@@ -0,0 +1,8 @@
+# 项目额外页面
+## Offer 与进阶
+- [我的 Offer 在哪里？](https://doocs.gitee.io/advanced-java/#/docs/extra-page/offer)
+- [让我们同步进阶！](https://doocs.gitee.io/advanced-java/#/docs/extra-page/advanced)
+
+## 项目 Page 页
+- [GitHub Page](https://doocs.github.io/advanced-java/#/)
+- [Gitee Page](https://doocs.gitee.io/advanced-java/#/)

index.html

@@ -26,10 +26,10 @@
         <ul>
           <li><a href="#">封面</a></li>
           <li><a href="#/README">首页</a></li>
-          <li><a href="#/advanced">进阶</a></li>
-          <li><a href="#/offer">Offer</a></li>
-          <li><a href="https://github.com/doocs">Doocs</a></li>
-          <li><a href="https://github.com/yanglbme">Author</a></li>
+          <li><a href="#/docs/extra-page/advanced">进阶</a></li>
+          <li><a href="#/docs/extra-page/offer">Offer</a></li>
+          <li><a href="https://github.com/doocs" target="_blank">Doocs</a></li>
+          <li><a href="https://github.com/yanglbme" target="_blank">Author</a></li>
         </ul>
       </li>
     </ul>
@@ -44,7 +44,7 @@
       auto2top: true,
       loadNavbar: false,
       coverpage: true,
-      coverpage: 'cover.md',
+      coverpage: 'docs/extra-page/cover.md',
       mergeNavbar: true,
       search: [
         '/'