Currencies are a bit strange; the layout of currency data in the CLDR is
not particularly compatible with what ECMA-402 expects. For example, the
currency format in the "en" and "ar" locales for the Latin script are:
en: "¤#,##0.00"
ar: "¤\u00A0#,##0.00"
Note how the "ar" locale has a non-breaking space after the currency
symbol (¤), but "en" does not. This does not mean that this space will
appear in the "ar"-formatted string, nor does it mean that a space won't
appear in the "en"-formatted string. This is a runtime decision based on
the currency display chosen by the user ("$" vs. "USD" vs. "US dollar")
and other rules in the Unicode TR-35 spec.
ECMA-402 shies away from the nuances here with "implementation-defined"
steps. LibUnicode will store the data parsed from the CLDR however it is
presented; making decisions about spacing, etc. will occur at runtime
based on user input.
There is quite a lot to be done here so this is just a first pass at
number formatting. Decimal and percent formatting are mostly working,
but only for standard and compact notation (engineering and scientific
notation are not implemented here). Currency formatting is parsed, but
there is more work to be done to handle e.g. using symbols instead of
currency codes ("$" instead of "USD"), and putting spaces around the
currency symbol ("USD 2.00" instead of "USD2.00").
This method represents the Intl.NumberFormat's [[RelevantExtensionKeys]]
internal slot, so it makes more sense for this to be directly in the
class itself.
