the value in format and formatToParts currently perform a ToNumber(value).
With the BigInt support specified in https://github.com/tc39/ecma402/pull/236 , we should also allow the value in Intl.RelativeTimeFormat.prototype.format and Intl.RelativeTimeFormat.prototype.formatToParts to be BigInt.
@littledan
the value in format and formatToParts currently perform a ToNumber(value). With the BigInt support specified in https://github.com/tc39/ecma402/pull/236 , we should also allow the value in Intl.RelativeTimeFormat.prototype.format and Intl.RelativeTimeFormat.prototype.formatToParts to be BigInt. @littledan