add gettext step to docker file

Dockerfile

@@ -26,7 +26,7 @@ COPY lib lib
 COPY priv priv
 COPY assets assets
 RUN npm run --prefix ./assets deploy
-RUN mix phx.digest
+RUN mix do phx.digest, gettext.extract
 
 # compile and build release
 # uncomment COPY if rel/ exists
@@ -50,4 +50,4 @@ COPY --from=build /app/priv/ /app/priv
 
 ENV HOME=/app
 
-CMD ["bin/lokal", "start"]
+CMD ["bin/lokal", "start"]