Adds documentation for WordPress.WP.CronInterval

[NielsdeBlaauw]

Related to #1722

[jrfnl]

Hi @NielsdeBlaauw Lekker bezig!

Loved seeing those five PRs coming in.

Reviewed this one and - aside from some nitpicks - there are two points which need attention. Note: these points may well also apply to the other doc PRs you send in:

1. Complying with the coding standards for the examples

Aside from the issue being demonstrated, the code samples should comply with the WP Coding Standards.
That means that closures as callbacks for filter hooks are not allowed (as they can't be unhooked).

While the sniff should still detect these kind of issues, even in code which doesn't comply with the standards, the example code used in the documentation should be "clean".

2. Highlighting of the important bits

The particular bit in the code which is the actual "problem" should be wrapped in <em> tags which will allow the code to be highlighted when the HTML/Markdown generators are used.

[NielsdeBlaauw]

Ah yes, noticed the <em>'s when viewing another item just now. I'll take the review for this pul requests to all others, so don't bother reviewing those at this time. They'll receive a update tomorrow.

[jrfnl]

@NielsdeBlaauw Excellent! Thanks. The same goes for your earlier PR #1730, so if you have a chance to update that one too.... 😇

[jrfnl]

... so don't bother reviewing those at this time. They'll receive a update tomorrow.

Haven't done a full review of any of them, but I did just have a quick look and left some small remarks here and there which might be helpful for when you are updating the PRs tomorrow anyway.

[jrfnl]

LGTM. Thanks for updating it!