tweak issue template

Author: yihui

.github/ISSUE_TEMPLATE.md

@@ -1,3 +1,12 @@
+
+
+
+<!--
+Please keep the below portion in your issue and delete the portion below. Your issue will be closed if any of the above boxes is not checked. In certain (rare) cases, you may be exempted if you give a brief explanation (e.g., you are only making a suggestion for improvement). Thanks!
+-->
+
+---
+
 By filing an issue to this repo, I promise that
 
 - [ ] I have fully read the issue guide at https://yihui.name/issue/.
@@ -7,6 +16,4 @@ By filing an issue to this repo, I promise that
     - If I have posted the same issue elsewhere, I have also mentioned it in this issue.
 - [ ] I have learned the Github Markdown syntax, and formatted my issue correctly.
 
-<!--
-Please keep the above portion in your issue and delete the portion below. Your issue will be closed if any of the above boxes is not checked. In certain (rare) cases, you may be exempted if you give a brief explanation (e.g., you are only making a suggestion for improvement). Thanks!
--->
+I understand that my issue may be closed if I don't fulfill my promises.