Update installation guide with offline installation note

Added note recommending offline installation for production environments.

Author: maninhill

docs/installation/online_installtion.md

@@ -1,4 +1,7 @@
 ## 1 部署要求
+    
+!!! Abstract ""
+    如果用于生产环境，离线安装是官方推荐的安装方式。
 
 ### 1.1 服务器配置