You can now set the keyboard layout and language. Eg.
[customizations.locale]
languages = ["en_CA.utf8", "en_HK.utf8"]
keyboard = "de (dvorak)"
Existing entries in the kickstart templates are replaced with the new
ones. If there are no entries then it will default to 'keyboard us' and
'lang en_US.UTF-8'
Includes tests, and leaves the existing keyboard and lang entries in the
templates with a note that they can be replaced by the blueprint.
