Add security policy document

SECURITY.md

@@ -0,0 +1,18 @@
+# Security Policy
+
+## Supported Versions
+
+Security issues affecting older versions of this software are out of scope.
+
+| Version | Supported          |
+|---------| ------------------ |
+| 2.3.x   | :white_check_mark: |
+| < 2.3   | :x:                |
+
+## Reporting a Vulnerability
+
+To inform us of a security issue in our library, please email `security at pargonie dot com`
+with the details of your security concern.
+
+Unlike most software projects, we won't get offended if you drop the details into a GitHub issue.
+Protecting users is more important to us than anything else.