use copilot to generate pr content

.github/PULL_REQUEST_TEMPLATE.md

@@ -1,7 +1,7 @@
 
 - [ ] Make sure you have followed [Kube-OVN Code Style](https://github.com/kubeovn/kube-ovn/blob/master/CODE_STYLE.md).
 
-#### What type of this PR
+### What type of this PR
 Examples of user facing changes:
 - Features
 - Bug fixes
@@ -11,5 +11,13 @@ Examples of user facing changes:
 Describe your changes here, ideally you can get that description straight from your descriptive commit message(s)!
 -->
 
-#### Which issue(s) this PR fixes:
+### Which issue(s) this PR fixes:
 Fixes #(issue-number)
+
+### WHAT
+copilot:summary
+
+copilot:poem
+
+### HOW
+copilot:walkthrough