Update README.md (#1749)

udpate related url

README.md

@@ -58,25 +58,25 @@ Overload processing: Task queue mechanism, the number of schedulable tasks on a
 
 ### Document
 
-- <a href="https://dolphinscheduler.apache.org/en-us/docs/user_doc/backend-deployment.html" target="_blank">Backend deployment documentation</a>
+- <a href="https://dolphinscheduler.apache.org/en-us/docs/1.2.0/user_doc/backend-deployment.html" target="_blank">Backend deployment documentation</a>
 
-- <a href="https://dolphinscheduler.apache.org/en-us/docs/user_doc/frontend-deployment.html" target="_blank">Front-end deployment documentation</a>
+- <a href="https://dolphinscheduler.apache.org/en-us/docs/1.2.0/user_doc/frontend-deployment.html" target="_blank">Front-end deployment documentation</a>
 
-- [**User manual**](https://dolphinscheduler.apache.org/en-us/docs/user_doc/system-manual.html?_blank "System manual")
+- [**User manual**](https://dolphinscheduler.apache.org/en-us/docs/1.2.0/user_doc/system-manual.html?_blank "System manual")
 
-- [**Upgrade document**](https://dolphinscheduler.apache.org/en-us/docs/release/upgrade.html?_blank "Upgrade document")
+- [**Upgrade document**](https://dolphinscheduler.apache.org/en-us/docs/1.2.0/release/upgrade.html?_blank "Upgrade document")
 
 - <a href="http://106.75.43.194:8888" target="_blank">Online Demo</a>
 
-More documentation please refer to <a href="https://dolphinscheduler.apache.org/en-us/docs/user_doc/quick-start.html" target="_blank">[DolphinScheduler online documentation]</a>
+More documentation please refer to <a href="https://dolphinscheduler.apache.org/en-us/docs/1.2.0/user_doc/quick-start.html" target="_blank">[DolphinScheduler online documentation]</a>
 
 ### Recent R&D plan
 Work plan of Dolphin Scheduler: [R&D plan](https://github.com/apache/incubator-dolphinscheduler/projects/1), Under the `In Develop` card is what is currently being developed, TODO card is to be done (including feature ideas)
 
-### How to contribute code
+### How to contribute
 
-Welcome to participate in contributing code, please refer to the process of submitting the code:
-[[How to contribute code](https://github.com/apache/incubator-dolphinscheduler/issues/310)]
+Welcome to participate in contributing, please refer to the process of submitting the code:
+[[How to contribute](https://dolphinscheduler.apache.org/en-us/docs/development/contribute.html)]
 
 ### How to Build