Add PagerDuty Incident Response Documentation

README.md

@@ -145,6 +145,7 @@ A curated list of tools and resources for security incident response, aimed to h
 
 * [Demisto Playbooks Collection](https://www.demisto.com/category/playbooks/) - Playbooks collection
 * [IR Workflow Gallery](https://www.incidentresponse.com/playbooks/) - Different generic incident response workflows, e.g. for malware outbreak, data theft, unauthorized access,... Every workflow constists of seven steps: prepare, detect, analyze, contain, eradicate, recover, post-incident handling. The workflows are online available or for download
+* [PagerDuty Incident Response Documentation](https://response.pagerduty.com/) - Documents that describe parts of the PagerDuty Incident Response process. It provides information not only on preparing for an incident, but also what to do during and after. Source is available on [GitHub](https://github.com/PagerDuty/incident-response-docs).
 
 ### Process Dump Tools