Add note about DTR to registry description

registry/content.md

@@ -28,3 +28,7 @@ $ docker run \
 ```
 
 NOTE: The container will try to allocate the port 5000. If the port is already taken, find out which container is already using it by running `docker ps`.
+
+# Support
+
+If you are interested in commercial support, the [Docker Trusted Registry](https://www.docker.com/docker-trusted-registry) provides an image registry, LDAP/Active Directory integration, security certificates, and more in a solution that includes commercial support.