Add pr templates.

Author: wushengyeyouya

.github/PULL_REQUEST_TEMPLATE.md

@@ -0,0 +1,28 @@
+### What is the purpose of the change
+(For example: AppConn Core defines the abstractions and interfaces of the AppConn core functions.
+It is the core concept that enables DSS to easily and quickly integrate various upper-layer web systems.
+Related issues: #590. )
+
+### Brief change log
+(for example:)
+- Define the core abstraction and interfaces of the AppConn;
+- Define the core abstraction and interfaces of the three-level specifications of AppConn.
+
+### Verifying this change
+(Please pick either of the following options)  
+This change is a trivial rework / code cleanup without any test coverage.  
+(or)  
+This change is already covered by existing tests, such as (please describe tests).  
+(or)  
+This change added tests and can be verified as follows:  
+(example:)  
+- Added tests for creating and execute the workflow contains the nodes that DSS has integrated to go through and verify the availability of different AppConns.
+
+### Does this pull request potentially affect one of the following parts:
+- Dependencies (does it add or upgrade a dependency): (yes / no)
+- Anything that affects deployment: (yes / no / don't know)
+- The Core framework, i.e., AppConn, Orchestrator, ApiService.: (yes / no)
+
+### Documentation
+- Does this pull request introduce a new feature? (yes / no)
+- If yes, how is the feature documented? (not applicable / docs / JavaDocs / not documented)