Update section on multiple h1 elements per page

[robinmetral]

Summary

Update the section on the Heading Elements page to reflect the recent change to the HTML spec.

In a nutshell, to create a heading outline...

<main>
  <h1>Page title</h1>
  <section>
    <h1>Section title</h1> <!-- 🙅 don't do this -->
    <h2>Section title</h2> <!-- ✅ do this -->
  </section
</main>

Motivation

Make it clear that relying on the outline algorithm isn't only bad practice, it doesn't follow the spec.

Supporting details

• PR to the HTML spec
• Good article with full timeline and recent updates by Adrian Roselli: There Is No Document Outline Algorithm

Related issues

Related to #18530 (caused by the same change to the HTML spec)

Metadata

• Adds a new document
• Rewrites (or significantly expands) a document
• Fixes a typo, bug, or other error

[github-actions]

Preview URLs

• /en-US/docs/Web/HTML/Element/Heading_Elements

Flaws

URL: /en-US/docs/Web/HTML/Element/Heading_Elements
Title: <h1>–<h6>: The HTML Section Heading elements
Flaw count: 1

• macros:
  • wrong xref macro used (consider changing which macro you use)

External URLs

URL: /en-US/docs/Web/HTML/Element/Heading_Elements
Title: <h1>–<h6>: The HTML Section Heading elements

• https://adrianroselli.com/2016/08/there-is-no-document-outline-algorithm.html (1 time) (Note! This may be a new URL 👀)

(this comment was updated 2022-09-22 05:36:16.996214)

[robinmetral]

Extra details 👇

[sideshowbarker]

@stevefaulkner could you please give this one a review?

[debiru]

refs. mdn/mdn-community#232