Some projects are missing `.gitlab-ci.yml`

e.g. apps/xfce4-mixer and apps/xfce4-volumed-pulse, maybe there are others. I realized this when pushing apps/xfce4-mixer!3 (merged).

Is it intentional?

EDIT: some more: xfce4-calculator-plugin, xfce4-mailwatch-plugin, xfce4-sensors-plugin, xfce4-whiskermenu-plugin.