Update pull_request_template.md

Author: tghosth

.github/pull_request_template.md

@@ -3,6 +3,7 @@ IMPORTANT NOTES:
 - Changes should always be made only in the raw .md files and not in the CSV, JSON, XLSX, PDF, DOCX files, etc.
 - Please do not open a pull request without first opening an associated issue.
 - Please carry out all discussion in the associated issue only.
+- Please refer to the following link for guidance on labeling contributions https://github.com/OWASP/ASVS/blob/master/CONTRIBUTING.md
 -->
 
 This Pull Request relates to issue #...