Optionally run as another user/group only if
the env vars are specified. Should give flexibility
to those who need to run processes as root and open ports
without having to request additional priveleges
with PUID and PGID environment variables
- Detects if image is run with a user in docker command and fails if so
- Adds s6 prepare scripts for adding a 'npmuser'
- Split up and refactor the s6 prepare scripts
- Runs nginx and backend node as 'npmuser'
- Changes ownership of files required at startup
