chore: allow issue template to be previewed for the link

close #1491

Author: yyx990803

.github/ISSUE_TEMPLATE.md

@@ -1,10 +1,8 @@
-<!--
 IMPORTANT: Please use the following link to create a new issue:
 
-  https://new-issue.vuejs.org/?repo=vuejs/vue-cli
+https://new-issue.vuejs.org/?repo=vuejs/vue-cli
 
 If your issue was not created using the app above, it will be closed immediately.
 
 中文用户请注意：
 请使用上面的链接来创建新的 issue。如果不是用上述工具创建的 issue 会被自动关闭。
--->