Create Security Policy (#329)

Author: diogoteles08

SECURITY.md

@@ -0,0 +1,13 @@
+# Security Policy
+
+## Supported Versions
+
+Security updates are applied only to the latest release.
+
+## Reporting a Vulnerability
+
+If you have discovered a security vulnerability in this project, please report it privately. **Do not disclose it as a public issue.** This gives us time to work with you to evaluate and fix the issue before public exposure, reducing the chance that the exploit will be used before a patch is released.
+
+Please disclose it at our [security advisory](https://github.com/golang/appengine/security/advisories/new).
+
+This project is maintained by a team of volunteers on a reasonable-effort basis. As such, vulnerabilities will be handled and/or disclosed in a best effort base.