Jest tests that illustrate various Javascript operations

Env vars. Have these set in your development shell or CI/CD environment.

export OPENAI_API_KEY = <openapi key>

Dev instructions

1. Install packages: yarn
2. Lint: yarn lint, yarn lintFix
3. Prettier: yarn pretty, yarn prettyFix
4. Run tests: yarn test
5. Run lint, prettier & tests: yarn all
6. Fix lint and prettier issues: yarn fix