Document various storage engine setups for the Quay operator

The documentation lacks examples on how to set up various storage engines to use with the Quay operator. We have this for the route component, but many customers prefer using their own storage solutions rather than using Noobaa. The documentation should be added under section 6.1:

https://access.redhat.com/documentation/en-us/red_hat_quay/3.4/html/deploy_red_hat_quay_on_openshift_with_the_quay_operator/advanced_concepts#customizing_external_access_to_the_registry

This is an example of the configuration for a Ceph compatible storage engine:

DISTRIBUTED_STORAGE_CONFIG:   default:   - RadosGWStorage
  - access_key: ACCESS_KEY_HERE
    bucket_name: BUCKET_NAME_HERE
    hostname: HOSTNAME_OR_IP_ADDRESS
    is_secure: false # this is by default, switch to true if you use SSL
    port: 'PORT_NUMBER'
    secret_key: SECRET_KEY_HERE
    storage_path: /datastorage/registry
DISTRIBUTED_STORAGE_DEFAULT_LOCATIONS: []
DISTRIBUTED_STORAGE_PREFERENCE: - default

However, we're still missing setups for AWS S3, Google, Swift and Azure.