HTML API: Add support for group of containers including ARTICLE element

[dmsnell]

There are a handful of elements which behave similarly and are generically
container elements. These are the following elements:

ADDRESS, ARTICLE, ASIDE, BLOCKQUOTE, CENTER, DETAILS, DIALOG, DIR,
DL, DIV, FIELDSET, FIGCAPTION, FIGURE, FOOTER, HEADER, HGROUP, MAIN,
MENU, NAV, SEARCH, SECTION, SUMMARY

This patch adds support to the HTML Processor for handling these elements.
They do not require any additional logic in the rest of the class, and carry
no specific semantic rules for parsing beyond what is listed in their group
in the IN BODY section of the HTML5 specification

Trac ticket: Core-59914

There are a handful of elements the behave similarly and are generically
container elements. These are the following elements:

ADDRESS, ARTICLE, ASIDE, BLOCKQUOTE, CENTER, DETAILS, DIALOG, DIR,
DL, DIV, FIELDSET, FIGCAPTION, FIGURE, FOOTER, HEADER, HGROUP, MAIN,
MENU, NAV, SEARCH, SECTION, SUMMARY,

This patch adds support to the HTML Processor for handling these elements.
They do not require any additional logic in the rest of the class, and carry
no specific semantic rules for parsing beyond what is listed in their group
in the IN BODY section of the HTML5 specification

[Bernhard Reiter]

In 57115:

HTML API: Add support for containers elements, including ARTICLE.

There are a handful of elements which behave similarly and are generically container elements. These are the following elements:

ADDRESS, ARTICLE, ASIDE, BLOCKQUOTE, CENTER, DETAILS, DIALOG, DIR,
DL, DIV, FIELDSET, FIGCAPTION, FIGURE, FOOTER, HEADER, HGROUP, MAIN,
MENU, NAV, SEARCH, SECTION, SUMMARY

This patch adds support to the HTML Processor for handling these elements. They do not require any additional logic in the rest of the class, and carry no specific semantic rules for parsing beyond what is listed in their group in the IN BODY section of the HTML5 specification.

Props dmsnell.
Fixes #59914.

BTW really appreciate the test coverage -- they're easy to read and follow, and provide a lot of confidence in the code changes! 🙌

Committed to Core in https://core.trac.wordpress.org/changeset/57115.

[stevenlinx]

as part of a standalone dev note post