Derives weekend days (0=Sun … 6=Sat) from a BCP 47 code. Uses Intl.Locale.getWeekInfo() where available, with a CLDR-based fallback table.
Intl.Locale.getWeekInfo()
A BCP 47 language tag (e.g. 'en-US', 'de-DE').
'en-US'
'de-DE'
An array of weekend day indices (sorted ascending).
Derives weekend days (0=Sun … 6=Sat) from a BCP 47 code. Uses
Intl.Locale.getWeekInfo()where available, with a CLDR-based fallback table.