chore(CONTRIBUTING.md): fix spelling mistake

CONTRIBUTING.md

@@ -4,7 +4,7 @@ Thank you for taking time to contribute to Hugo blog awesome!
 
 Following the contribution guidelines helps both owners and contributors. The guidelines save time and hassle caused by improperly created pull requests or issues that might have to be rejected and re-submitted.
 
-## When to use issues
+## When to use issues?
 
 We prefer to use issues for reporting real 'issues' or bugs. For feature requests you can visit the [feature request section](https://github.com/hugo-sid/hugo-blog-awesome/discussions/categories/feature-requests) of Discussions and start a new thread.