update readme

README-EN.md

@@ -11,6 +11,11 @@ Hydro is a high-performance online judge system.
 It is easy to deploy (with install script), light weight and extensible.  
 Also see previous version at [vijos/vj4](https://github.com/vijos/vj4)
 
+Now we have a SaaS service running at [https://hydro.ac](https://hydro.ac). (Fully free of charge!)  
+You can easily have a glance at the features of the system and try it out.  
+You can also just use the service without self-hosting the system with the powerful `domain` feature.  
+Feel free to create an account and then navigate to `MyAccount > MyDomains > Create Domain` to create one.  
+
 [中文](https://hydro.js.org/)  
 
 [Open pre-configured test environment in Gitpod](https://gitpod.io/#https://github.com/hydro-dev/Hydro)  
@@ -18,8 +23,8 @@ Also see previous version at [vijos/vj4](https://github.com/vijos/vj4)
 ## Contact US
 
 QQ [3402182471](https://wpa.qq.com/msgrd?v=3&uin=3402182471&site=qq&menu=yes)  
-Hydro QQ Group: 1085853538  
-Discord [Hydro](https://discord.gg/c633mBUJwS)  
+Hydro QQ User Group: 1085853538  
+Telegram Group [@hydrodev](https://t.me/hydrodev)
 Telegram [@webpack_exports_undefined](https://t.me/webpack_exports_undefined)  
 
 ## License