Review information in `currency_iso.json` to ensure it's accurate

[clauderic]

It looks like certain currencies listed in currency_iso.json have inaccurate values, specifically, some currencies are listed as having subunit_to_unit: 1, yet also have a non-null decimal_mark 🤔

Similarly, there seems to be some discrepancy between what character the browser's Number.toLocaleString API returns for certain locales, for instance, for be-BY, the thousands separator is ,, whereas it's listed in currency_iso.json as

(1235.50).toLocaleString("be-BY", {currency: 'BYR', style: 'currency', currencyDisplay: 'symbol'})
// "BYR 1,236"

However, looking at the data for the Intl.js polyfill, it looks like the thousands separator is listed as , https://github.com/andyearnshaw/Intl.js/blob/master/locale-data/json/be-BY.json#L285 so I'm
not sure which is accurate 🤷‍♂️

[bdewater]

I'm pretty sure it's not. AFAIK the browser/OS data is from https://www.currency-iso.org/en/home/tables.html or https://www.unicode.org/repos/cldr/trunk/common/supplemental/supplementalData.xml (which uses the former as a basis)