refactor: docker build improvements

[dlouzan]

make docker build build the package locally instead of depending on the npm registry published version

[bufferoverflow]

great work, what about dumb-init is it worth to use?

[dlouzan]

@bufferoverflow I find that using an init process in a docker container is a good practice to avoid any issues with signal handling. Even if we currently just start a node process, it helps with future-proofing in case we modify the startup to handle more than one process.

There's a couple of alternatives in this field:

• dumb-init
• tini
• native --init support in docker since version 1.13, from the tini docs:

  NOTE: If you are using Docker 1.13 or greater, Tini is included in Docker itself. This includes all versions of Docker CE. To enable Tini, just pass the --init flag to docker run.

To make things a bit better right now, I'm pushing in a minute a change to this PR that actually installs dumb-init as checksummed apk, instead of downloading an executable from github. I guess that a the time this was written in verdaccio, there was still no ported apk package.

[bufferoverflow]

Very nice!