OL reversed boolean attr

I use a DJOT template of

{reversed=reversed}
1. Last place: This person
1. Another place: xxx
1. First place: xxx

And that sets the attr into

<ol reversed="reversed">
<li>
Last place: This person
</li>
<li>
Another place: xxx
</li>
<li>
First place: xxx
</li>
</ol>

Which is valid and works in all browsers:
https://developer.mozilla.org/en-US/docs/Web/HTML/Reference/Elements/ol#reversed

But htmlpurifier emits warnings:

Warning (512) : Attribute 'reversed' in element 'ol' not supported (for information on implementing this, see the support forums) [in /shared/httpd/sandbox/vendor/ezyang/htmlpurifier/library/HTMLPurifier/HTMLDefinition.php, line 372]

I believe that's a bug.

Both shorthand <ol reversed> and <ol reversed="reversed"> etc should be valid.
I used this list:

$config->set('HTML.Allowed', '...,ul[class],ol[start|type|reversed],li');

Start in library/HTMLPurifier/HTMLDefinition.php around line 372, where the unsupported reversed attribute warning is emitted. Review how the HTML.Allowed setting handles ol[start|type|reversed] and compare it with the HTML standard examples in the issue. Done means both reversed shorthand and reversed="reversed" are accepted without warnings.