- Add antergos-lightdm-config to packages.yaml so CI builds/publishes it
(referenced by packagechooser_dm.conf LightDM group; without it the
online installer hits 'target not found' for LightDM installs)
- show.qml: correct DE count (Nine -> Ten, list Plasma Minimal) and
replace the 'Two Modes of Installation' slide that still claimed an
offline mode that was removed