[JIRA] (OVIRT-1254) add to infra docs on supporting building containers in std ci

add to infra docs on supporting building containers in std ci ------------------------------------------------------------- Key: OVIRT-1254 URL: https://ovirt-jira.atlassian.net/browse/OVIRT-1254 Project: oVirt - virtualization made easy Issue Type: Task Reporter: eyal edri [Administrator] Assignee: infra Priority: High We now support building containers in standard CI. we need to document how a developer will use it and to give example the ovirt-container-engine once it works.