CI: restore CI test functionality

[msimerson]

• ci: add GHA workflows, test all LTS versions of node on ubuntu & macOS
  • preview the test output in the actions tab of my fork
• package.json: populate files, limit what get published to NPM
• deps(all): bump to latest versions
• fix tap syntax for v18
• chore: add tap output dirs to .gitignore
• ci: run minimal eslint on PRs. Fix lint issues

fixes #43