Add ThreatHunter playbook to the rules section

Author: 0x4D31

README.md

@@ -139,6 +139,7 @@
 - [Awesome YARA Rules](https://github.com/InQuest/awesome-yara#rules)
 - [Chronicle Detection Rules](https://github.com/chronicle/detection-rules) - Collection of YARA-L 2.0 sample rules for the Chronicle Detection API.
 - [GCP Security Analytics](https://github.com/GoogleCloudPlatform/security-analytics) - Community Security Analytics provides a set of community-driven audit & threat queries for Google Cloud.
+- [ThreatHunter-Playbook](https://github.com/OTRF/ThreatHunter-Playbook) - A community-driven, open-source project to share detection logic, adversary tradecraft and resources to make detection development more efficient.
 
 ## Dataset