Description of problem:

Docuementation to install the cluster using certificate is missing in the official doc 

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

4.12

With the release of 4.12 installation of the cluster on Azure is allowed using a certificate that is not given in the documentation

We can merge the upstream link[0] with the doc

When installing the cluster using certificate, we need to manually create cloud-credentials for which we have already raised a doc bug[1] to merge with official doc

[0] https://github.com/openshift/installer/pull/6505/files
[1] https://issues.redhat.com/browse/OCPBUGS-6001?filter=-3