fix: Wrong year format on start week in week-picker mode (fixes #1055)

Author: Jasenkoo

src/VueDatePicker/composables/defaults.ts

@@ -36,7 +36,7 @@ export const useDefaults = (props: AllPropsType | PickerBasePropsType) => {
         if (props.format) return props.format as string;
         if (props.monthPicker) return 'MM/yyyy';
         if (props.timePicker) return getTimeFormat();
-        if (props.weekPicker) return `${defaultedWeekNumbers.value?.type === 'iso' ? 'RR' : 'ww'}-yyyy`;
+        if (props.weekPicker) return `${defaultedWeekNumbers.value?.type === 'iso' ? 'II' : 'ww'}-RR`;
         if (props.yearPicker) return 'yyyy';
         if (props.quarterPicker) return 'QQQ/yyyy';
         return props.enableTimePicker ? `MM/dd/yyyy, ${getTimeFormat()}` : 'MM/dd/yyyy';