docs: add SECURITY.md

Author: char0n

SECURITY.md

@@ -0,0 +1,18 @@
+# Security Policy
+
+If you believe you've found an exploitable security issue in openapi-runtime-expression, please don't create a public issue.
+
+## Supported Versions
+
+Use this section to tell people about which versions of your project are
+currently being supported with security updates.
+
+| Version | Supported          |
+| ------- | ------------------ |
+| 3.x.y   | :white_check_mark: |
+
+## Reporting a Vulnerability
+
+To report a vulnerability please send an email with the details to [email protected].
+
+I'll acknowledge receipt of your report ASAP, and set expectations on how I plan to handle it.