Local Week year is wrong on Firefox for en-US, fr-CA (locales with weeks starting on Sunday).

[JeanMeche]

I'm opening this bug for tracking purposes,

Currently the week year format (iiii) can be wrong on firefox because it doesn't support getWeekInfo and Luxon uses the following fallback (which is the ISO definition I believe):

luxon/src/impl/locale.js

Lines 320 to 324 in 3125686

	const fallbackWeekSettings = {
	firstDay: 1,
	minimalDays: 4,
	weekend: [6, 7],
	};