Dockerfile misses correct permissions in build step.

[almereyda]

The Dockerfile's build step does not yet apply the UID 9999, why the .next folder will be unreadable by yarn start.

I'm circumventing this with a custom Dockerfile:

FROM ohmyform/ui
USER root
RUN chown -R 9999:9999 /usr/src/app
USER ohmyform