Upgrade cli package to commander 7
commander is the library Antora uses to build its CLI. Antora currently uses commander 6. The upgrade to commander 7 was held back because it has major API changes. We need to sort through these changes, make the necessary updates, and get the tests working with commander 7 before we can upgrade.
See https://github.com/tj/commander.js/blob/master/CHANGELOG.md
Edited by Dan Allen