Writes theme.pot from the strings in the theme config.
mix gamend.theme.extract # write the template
mix gamend.theme.extract --check # fail if it is out of date
mix gamend.theme.extract -o PATH # write somewhere elsemix gettext.extract cannot find these: it scans source for gettext(...)
calls, and theme text lives in data. This walks the config instead, using the
same Gamend.Theme.Translatable list the renderer uses, so the strings a
translator is offered are exactly the strings the server will translate.
Merge into the per-locale PO files afterwards the usual way:
mix gettext.merge priv/gettext