chore(.nvmrc): update to 'lts/iron' for ESLint compatibility and add related comment

[sukvvon]

Overview

• Updated the .nvmrc file to use lts/iron to meet ESLint’s minimum requirements.
• ESLint requires at least Node.js 20.9.0, so the iron release line now explicitly uses a compatible version.
  • https://eslint.org/docs/latest/use/getting-started#prerequisites
• Included a link to the ESLint official documentation.

Checklist

• Did you write the test code?
• Have you run yarn run fix to format and lint the code and docs?
• Have you run yarn run test:coverage to make sure there is no uncovered line?
• Did you write the JSDoc?

[seungrodotlee]

Thanks! 👍