Add compatibility with PHP 8.4 Dom\HTMLDocument

[ddebin]

Inspired by #5, keep backward DOMDocument compatibility for PHP <8.4.
I can add a PR to brick/schema (to allow passing a Dom\Document) if accepted.

[adamjgriffith]

@ddebin Firstly thanks for picking this up!

FYI I left the afformentioned PR in draft because my understanding of using the HTML_NO_DEFAULT_NS constant nullifies most of the advantages of the new PHP 8.4 DOM classes and my needs moved on from this package.

It is also possible to pass Dom\HTML_NO_DEFAULT_NS to disable the use of the HTML namespace and the template element. This should only be used if the implications are properly understood.

From https://www.php.net/manual/en/dom-htmldocument.createfromstring.php

Do you properly understand the implications of using this constant?

[ddebin]

@adamjgriffith I'm not an expert. I see this option as a way to treat HTML5 as a proper XML DOM, but it's not. Per https://stackoverflow.com/a/79443754/377645, it seems HTML_NO_DEFAULT_NS should have been the default way, as 99% of cases need this option.

[ddebin]

Some explanation here:

To ease migration from HTML to XML, user agents conforming to this specification will place elements in HTML in the http://www.w3.org/1999/xhtml namespace, at least for the purposes of the DOM and CSS. The term "HTML elements" refers to any element in that namespace, even in XML documents.

With HTML_NO_DEFAULT_NS, HTML elements are not placed in this namespace. It may impact the way of parsing and the DOM structure, but in this project, parsing is done (example) without a namespace.