Add guideline link into DolphinScheduler mail list (apache#15447)

Co-authored-by: Jay Chung <zhongjiajie955@gmail.com>
Co-authored-by: fuchanghai <changhaifu@apache.org>

README.md

@@ -66,7 +66,7 @@ Welcome to join the Apache DolphinScheduler community by:
 
 - Join the [DolphinScheduler Slack](https://s.apache.org/dolphinscheduler-slack) to keep in touch with the community
 - Follow the [DolphinScheduler Twitter](https://twitter.com/dolphinschedule) and get the latest news <!-- markdown-link-check-disable-line -->
-- Subscribe DolphinScheduler mail list, users@dolphinscheduler.apache.org for user and dev@dolphinscheduler.apache.org for developer
+- Subscribe DolphinScheduler mail list, [users@dolphinscheduler.apache.org](mailto:users-subscribe@dolphinscheduler.apache.org) for user and [dev@dolphinscheduler.apache.org](mailto:dev-subscribe@dolphinscheduler.apache.org) for developer
 
 # Landscapes
 

README_zh_CN.md

@@ -62,7 +62,7 @@ DolphinScheduler 的主要特性如下：
 
 - 加入 [DolphinScheduler Slack](https://s.apache.org/dolphinscheduler-slack)
 - 关注 [DolphinScheduler Twitter](https://twitter.com/dolphinschedule) 来获取最新消息 <!-- markdown-link-check-disable-line -->
-- 订阅 DolphinScheduler 邮件列表, 用户订阅 users@dolphinscheduler.apache.org 开发者请订阅 dev@dolphinscheduler.apache.org
+- 订阅 DolphinScheduler 邮件列表, 用户订阅 [users@dolphinscheduler.apache.org](mailto:users-subscribe@dolphinscheduler.apache.org) 开发者请订阅 [dev@dolphinscheduler.apache.org](mailto:dev-subscribe@dolphinscheduler.apache.org)
 
 # Landscapes