Upgrade Node.js to 12.14.0, add @silvermine/standardization and related tooling

[pbredenberg]

In this PR:

• Node.js upgrades, including check-node-version
• added @silvermine/standardization, upgraded our ESLint stack
• configured markdownlint and fixed some resulting linter error in README.md

I also upgraded the Dockerfile and docker-compose configuration. I believe I did it right, seemed to build ok using Node's official 12.14.0 image, but might not be a bad idea to make sure it's doing what we're expecting it to do.

That is all.