Update .github/workflows/pull_request_template.md

Co-authored-by: Novus Nota <68142933+novusnota@users.noreply.github.com>

.github/workflows/pull_request_template.md

@@ -1,4 +1,9 @@
-Closes issue #number
+Closes #number
+
+<!--
+IMPORTANT:
+If your PR doesn't close a particular issue, please, create the issue first and describe the whole context: what you're adding/changing and why you're doing so. And only then open the Pull Request, which would close that issue!
+-->
 
 * [ ] I have updated CHANGELOG.md
 * [ ] I have added unit tests to check possible regressions (if your PR introduces new error messages, each of those should have a distinct test case)