Add Security Policy

As the title says

Signed-off-by: TomSweeneyRedHat <tsweeney@redhat.com>

SECURITY.md

+## Security and Disclosure Information Policy for the dnsname Project
+
+The dnsname Project follows the [Security and Disclosure Information Policy](https://github.com/containers/common/blob/master/SECURITY.md) for the Containers Projects.