Add PluralRules selectRange about proposal-intl-numberformat-v3

[eemeli]

I can probably expand my intl-pluralrules polyfill to support this. @sffc please let me know once there's something like a spec to start playing around with?

[jswalden]

UTS 35 briefly discusses plural rules for ranges: https://unicode.org/reports/tr35/tr35-numbers.html#Plural_Ranges

[sffc]

The spec is here:

https://unicode.org/reports/tr35/tr35-numbers.html#Plural_Ranges

The data is here:

https://github.com/unicode-org/cldr/blob/master/common/supplemental/pluralRanges.xml

[eemeli]

By spec I actually meant a spec for the PluralRules.prototype.selectRange()JS function, but I can presume that it's something like (start: number, end: number): 'zero'|'one'|'two'|'few'|'many'|'other' to start with, and make up stuff about errors.

As a first step I'll need to add the data to make-plural, which is what intl-pluralrules internally uses. While starting at that, I noticed that the cldr-core npm package does not include the pluralRanges data. I'll add a ticket on the CLDR Jira about this.