Merge pull request #5257 from savitharaghunathan/add_sig_security_docs

Adding sig-security-docs slack channel

Author: k8s-ci-robot

communication/slack-config/channels.yaml

@@ -338,6 +338,7 @@ channels:
   - name: sig-scalability
   - name: sig-scheduling
   - name: sig-security
+  - name: sig-security-docs
   - name: sig-security-tooling
   - name: sig-service-catalog
   - name: sig-testing