[12.x] Add daysOfMonth to scheduling (#10922)

* add `daysOfMonth` to scheduling

* Update daysOfMonth description in scheduling.md

Clarified the description for the daysOfMonth method.

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Co-authored-by: Taylor Otwell <taylor@laravel.com>

Author: milwad-dev

scheduling.md

@@ -168,6 +168,7 @@ We've already seen a few examples of how you may configure a task to run at spec
 | `->dailyAt('13:00');`              | Run the task every day at 13:00.                         |
 | `->twiceDaily(1, 13);`             | Run the task daily at 1:00 & 13:00.                      |
 | `->twiceDailyAt(1, 13, 15);`       | Run the task daily at 1:15 & 13:15.                      |
+| `->daysOfMonth([1, 10, 20]);`      | Run the task on specific days of the month.              |
 | `->weekly();`                      | Run the task every Sunday at 00:00.                      |
 | `->weeklyOn(1, '8:00');`           | Run the task every week on Monday at 8:00.               |
 | `->monthly();`                     | Run the task on the first day of every month at 00:00.   |