Add offline installation documentation link

Author: maninhill

mkdocs.yml

@@ -43,6 +43,7 @@ nav:
   - 安装部署:
     - 在线安装: installation/online_installation.md
     - 在线升级: installation/online_upgrade.md
+    - 离线安装：installation/package_installation.md
     - 从 V1 版本升级:
       - 升级说明: installation/v1_migrate.md
       - 操作步骤: installation/v1_migrate_steps.md