Intl.DisplayNames.prototype.of should return string | undefined

[tao-cumplido]

Bug Report

🔎 Search Terms

• intl
• displaynames

🕗 Version & Regression Information

The type information didn't exist before 4.5
PR by @orta #45647

🙁 Actual behavior

Intl.DisplayNames.prototype.of returns string in lib.es2020.intl.d.ts

🙂 Expected behavior

It should return string | undefined
See spec https://tc39.es/ecma402/#sec-Intl.DisplayNames.prototype.of

[orta]

Yep, agree, open to PRs for this 👍🏻