*: format, refactor, and update

[VoltrexKeyva]

• Change code style from StandardJS to Prettier-like style.
• Format all the code.
• Use ESLint for linting JavaScript code.
• Add package-lock.json file to .gitignore.
• Refactor code and tests.
• Add format NPM script to format code (npm run format).
• Update dependencies to their latest version.
• Rename readme.md to README.md to assert convention consistency.

BREAKING:

• Drop support for Node.js v10 and v12.
• Move to pure ESM.