Merge pull request #948 from buildkite/keithduncan/add-security.md

Create SECURITY.md

Author: keithduncan

SECURITY.md

@@ -0,0 +1,16 @@
+# Security Policy
+
+## Supported Versions
+
+Security fixes are supported for the most recent major and minor
+version of the Elastic CI Stack for AWS.
+
+| Version | Supported          |
+| ------- | ------------------ |
+| 5.x.x   | :white_check_mark: |
+| < 5.0   | :x:                |
+
+## Reporting a Vulnerability
+
+If you have found a vulnerability, please see https://buildkite.com/security
+for details on where and how to report it.