Documentation for Docker Retention and Expiration Policies

As a part of the effort in creating retention and expiration policies for the docker container registry we need to create dedicated documentation and link to it in the user interface,

We would probably need to extend the following part of the documentation:

• Container Registry Admin Guide
• Container Registry User Guide
• Container Registry Garbage Collection

We will also need to properly link the new documentation part in the interface for an easy access experience for the user