Create SECURITY.md for GitHub security policy page

GitHub has a security policy page (https://github.com/kubernetes/kubernetes/security/policy)
that uses a SECURITY.md file from the repository to show the project's
security policy.

https://help.github.com/en/articles/adding-a-security-policy-to-your-repository

Author: praseodym

.github/SECURITY.md

@@ -0,0 +1,14 @@
+# Security Policy
+
+## Supported Versions
+
+Information about supported Kubernetes versions can be found on the
+[Kubernetes version and version skew support policy] page on the Kubernetes website.
+
+## Reporting a Vulnerability
+
+Instructions for reporting a vulnerability can be found on the
+[Kubernetes Security and Disclosure Information] page.
+
+[Kubernetes version and version skew support policy]: https://kubernetes.io/docs/setup/release/version-skew-policy/#supported-versions
+[Kubernetes Security and Disclosure Information]: https://kubernetes.io/docs/reference/issues-security/security/#report-a-vulnerability