CFE-4659: Added changelog-generator to cfengine-cli

Based on the previous changelog-scripts:
https://github.com/cfengine/cf-bottom/blob/master/tom/changelog.py and
https://github.com/cfengine/core/blob/master/misc/changelog-generator/changelog-generator

Made with the intention to easily integrate with gh-action workflow in
the future

Author: SimonThalvorsen