Description of problem:
Example for AgentServiceConfig CRD mirroring [1] is incorrect, missing a ca/registries.conf configmap example, and wording in the configmap explanation is confusing.

[1] https://github.com/openshift/assisted-service/blob/master/docs/operator.md#deploying-the-operand-with-mirror-registry-configuration


Version-Release number of selected component (if applicable):
Latest

How reproducible:
100%

Steps to Reproduce:
1.Read [1] 


Actual results:
N/A

Expected results:
N/A

Additional info:
(1) mirrorRegistryConfigmapName: mirrorRegistyMap is listed, when it should be
  mirrorRegistryRef:
    name: registry-ca
per the CRD

(2) The configmap wording is confusing - " but it is still one string registries.conf - contents of the registries.conf file that configures mapping to the mirror registry."

(3) An example of the configmap would help immensely