message: Add index information to `getDay` docs
diff: @@ -14,7 +14,7 @@ import requiredArgs from '../_lib/requiredArgs/index.js'
  * - [Changes that are common for the whole library](https://github.com/date-fns/date-fns/blob/master/docs/upgradeGuide.md#Common-Changes).
  *
  * @param {Date|Number} date - the given date
  - * @returns {0|1|2|3|4|5|6} the day of week
  + * @returns {0|1|2|3|4|5|6} the day of week, 0 represents Sunday
  * @throws {TypeError} 1 argument required
  *
  * @example
  