tasks-with-cron-jobs: explain the steps expression (#10540)

The `/` steps expression is used throughout this doc but is never explained. Worse, it isn't actually part of the "normal" Cron spec linked in Wikipedia and is an extension added to vixiecron

content/en/docs/tasks/job/automated-tasks-with-cron-jobs.md

@@ -130,6 +130,16 @@ A cron job config also needs a [`.spec` section](https://git.k8s.io/community/co
 The `.spec.schedule` is a required field of the `.spec`.
 It takes a [Cron](https://en.wikipedia.org/wiki/Cron) format string, such as `0 * * * *` or `@hourly`, as schedule time of its jobs to be created and executed.
 
+The format also includes extended `vixie cron` step values. As explained in the [FreeBSD manual](https://www.freebsd.org/cgi/man.cgi?crontab%285%29):
+
+> Step values can be	used in	conjunction with ranges.  Following a range
+> with ``/<number>''	specifies skips	of the number's	value through the
+> range.  For example, ``0-23/2'' can be used in the	hours field to specify
+> command execution every other hour	(the alternative in the	V7 standard is
+> ``0,2,4,6,8,10,12,14,16,18,20,22'').  Steps are also permitted after an
+> asterisk, so if you want to say ``every two hours'', just use ``*/2''.
+
+
 **Note:** The question mark (`?`) in the schedule has the same meaning as an asterisk `*`, that is, it stands for any of available value for a given field.
 
 ### Job Template