refactor: Extract variable weekInfo

Author: claremacrae

src/ui/Menus/DatePicker.ts

@@ -22,7 +22,8 @@ export function promptForDate(
     //      running overnight, the flatpickr modal shows the previous day as Today.
     // Try to determine the first day of the week based on the locale, or use Monday
     // if unavailable
-    const firstDayOfWeekFromLocale = (new Intl.Locale(navigator.language) as any).weekInfo.firstDay;
+    const weekInfo = (new Intl.Locale(navigator.language) as any).weekInfo;
+    const firstDayOfWeekFromLocale = weekInfo.firstDay;
     const firstDayOfWeek = firstDayOfWeekFromLocale ?? 1;
     const fp = flatpickr(parentElement, {
         defaultDate: currentValue ? currentValue.format('YYYY-MM-DD') : new Date(),