[JIRA] (OVIRT-2212) Document the steps needed to add a new distro for CI slaves

Document the steps needed to add a new distro for CI slaves ----------------------------------------------------------- Key: OVIRT-2212 URL: https://ovirt-jira.atlassian.net/browse/OVIRT-2212 Project: oVirt - virtualization made easy Issue Type: Task Components: Documentation, Jenkins Slaves Reporter: Evgheni Dereveanchin Assignee: infra Adding a new distro/architecture to CI involves multiple steps like installing software, creating users, managing software mirrors. This process needs to be documented on ReadTheDocs