getDaysInMonth
import { getDaysInMonth } from "https://esm.sh/v135/date-fns@3.6.0/index.d.mts";@example
// How many days are in February 2000?
const result = getDaysInMonth(new Date(2000, 1))
//=> 29
function getDaysInMonth<DateType extends Date>(date: DateType | number | string): number;