Proposal to change the headings hierarchy in the Plugins section

[afercia]

Splitting this out from #4110.

The headings hierarchy in the Plugins section has room for improvements for better SEO and accessibility:

As mentioned in #4112 the logo shouldn't be a h1. "Plugins" should be the only h1 in this page.

Most of the other headings are h2 and that may make sense at first sight.

However, this page is split in sections:

• "Block-Enabled Plugins" is a h2 thus all the plugins under it should be h3
• same for "Featured Plugins", "Beta Plugins", "My Favorites", "Popular Plugins": they're h2 thus all the plugins under them should be h3

Also, at the bottom of the page, the h3 headings:

• Add Your Plugin
• Create a Plugin
• Stay Up-to-Date

shouldn't be h3: this way, they're hierarchically under the last plugin in the page (Jetpack in this case) which is clearly incorrect, as they're logically related to the whole page.

"See all" pages:
In the related "See all" pages, for example ​https://wordpress.org/plugins/browse/featured/:

• "Browse: Featured" should be the only h1 in the page

Search results page:

• "Showing results for: {term}" should be the only h1 in the page

Plugin detail page:

• the plugin name should be the only h1 in the page
• some of the headings are parsed from the plugin's readme.txt, let's hope developers are using markdown correctly
• however, in the sidebar the following headings:
  • "Meta" (it's visually hidden with screen-reader-text)
  • "Ratings"
  • "Support"
  • "Donate" (if present)

shouldn't be h3: this way, they're hierarchically under the last heading in the description, which is incorrect because they're logically related to the plugin page as a whole. They should be h2. Example screenshot:

Please consider going through all the pages in this section is out of the scope of this ticket. However, these are general guidelines that should be applied everywhere.

[dufresnesteven]

Updates heading hierarchy on /plugins.

[dufresnesteven]

Outcome from 4115.diff

[dufresnesteven]

Update plugin details page headings

[tellyworth]

In 9735:

Plugin dir: improve the heading hierarchy.

Improvements for SEO and a11y.

Props dufresnesteven, afercia.
See #4115.

[tellyworth]

In 9736:

Plugin dir: improve heading hierarchy.

Theme changes for SEO and a11y.

Props afercia, dufresnesteven.
Fixes #4115.