🔒️ Address Security Policy

https://github.com/stoe/action-reporting-cli/security/code-scanning/8

.github/security.md

@@ -0,0 +1,6 @@
+# Security Policy
+
+If you discover a security issue in this repo, please open a [private security advisory](https://github.com/ststoe/action-reporting-cli/security/advisories/new).
+Please do not open a public issue.
+
+Thanks for helping make this project safe for everyone.