[8.x] Add yearlyOn() method to scheduler

[u01jmg3]

Premise

I need to run a task once a year on a specific month (when the university term ends). Currently there is no expressive way to accomplish this with the available frequency options.

As weeklyOn($day, $time) and monthlyOn($day, $time) already exist, I simply used them as a guide and created yearlyOn($month, $day, $time).

// https://crontab.guru/#0_0_1_7_*
// At 00:00 on day-of-month 1 in July.

// Before
$schedule->cron('0 0 1 7 *');

// After
$schedule->yearlyOn(7);

[GrahamCampbell]

I suppose other use cases for this would be generation of annual tax documents, and the like.