Needs work on Dockerfile

[j2l]

Hello,

A few things needs to be changed:
19.04 -> 20.04 because Ubuntu 19 was decommissioned (see https://askubuntu.com/questions/1238222/the-repository-http-security-ubuntu-com-ubuntu-disco-security-release-no-lon).

ENV TZ=Europe/Paris or else
...
RUN apt-get update
RUN apt-get install -y tzdata to prevent tz setup from stopping the build process and getting the TZ from ENV
...

After RUN mkdir /www/node_modules/:
RUN cd /wwwneeded to be sure we install in the right folder
RUN npm init -y needed for package.json

I had to change a few things to run+manage it with Portainer:
change auto-created container name to something permanent (TotalJS), its image to superadmin:1.5
manually add 8080 to 80
Interactive+TTY,
restart = until stopped