Update pluralization rules to v4

[williamhjcho]

https://www.i18next.com/translation-function/plurals
https://i18next.github.io/i18next-v4-format-converter-web/
https://github.com/i18next/i18next/blob/master/src/PluralResolver.js
https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Intl/PluralRules/PluralRules
https://docs.translatehouse.org/projects/localization-guide/en/latest/l10n/pluralforms.html?id=l10n/pluralforms
https://unicode-org.github.io/cldr-staging/charts/37/supplemental/language_plural_rules.html#rules