[JIRA] (OVIRT-1823) Document usrc.py

Document usrc.py ---------------- Key: OVIRT-1823 URL: https://ovirt-jira.atlassian.net/browse/OVIRT-1823 Project: oVirt - virtualization made easy Issue Type: Improvement Components: oVirt CI Reporter: Barak Korren Assignee: Barak Korren Priority: High Labels: poll-upstream-sources, standard-ci {{usrc.py}} is a local tool for using git repositories with upstream sources that are defined in '{{automation/upstream-sources.yaml}}'. We need some documentation about how to install and use this tool in our infra-docs.