Consider to audit the headings hierarchy across the .org network

[afercia]

Headings are important not only for semantics and SEO: they are actually used by screen reader users as the ​predominant mechanism to find information on a page.

For better accessibility, SEO, and semantics there are some best known practices, also recommended by the core accessibility team:

• a main h1 heading should be used to communicate the main page topic
• there should be only one h1 in a page
• the main topic of a page is rarely the site title, this is maybe true only on the home page (and it's still matter of debate)
• in all the other pages, the main h1 is meant to be used for that specific page topic
• headings needs to have a correct hierarchy: no levels should be skipped

There are different tools to check the headings structure of a page. For the purpose of this ticket, I've used the HeadingsMap Chrome extension. I've also collected a series of screenshots to illustrate the headings hierarchy in the main pages of the .org network as of today, January 28, 2018: ​https://cloudup.com/cCODexEIFbq

To recap:

• Home: two h1 and incorrect hierarchy
• Showcase: incorrect hierarchy
• Themes: two h1 and incorrect hierarchy
• Plugins: two h1
• Mobile: hierarchy OK but the main page topic is not a h1
• Support: two h1 and incorrect hierarchy
• Get involved (Make): two h1 and incorrect hierarchy
• About: two h1
• Blog: hierarchy OK but the main page topic is not a h1
• Hosting: hierarchy OK but the main page topic is not a h1

I realize the .org network is made of different templates coming from different sources and I guess it's a complicated setup. However, it would be great to make sure the headings hierarchy is correct on all the network pages.

[afercia]

As requested by Marketing & Communications, I'm going to split this ticket in separate tickets for each main .org section.

[afercia]

Update: the HeadingsMap extension is available for both Chrome and Firefox:

• ​https://chrome.google.com/webstore/detail/headingsmap/flbjommegcjonpdmenkdiocclhjacmbi
• ​https://addons.mozilla.org/en-US/firefox/addon/headingsmap/

[dd32]

When testing for these headers, it'd be advisable to use localised versions of the directories/etc as the rosetta headers will affect the overall hierarchy.

Right now it seems that the header being a <h1> is going to block most of the changes, sites like ​https://test.wordpress.org/ also have a <h2> there though.
Removing that h1/h2 is "easy" done if someone wants to suggest the alternate HTML and/or CSS to make it happen.

[dd32]

In 9725:

Theme Directory: Use better heading numbers for the Theme Directory.

Props afercia, poena, dufresnesteven, dd32.
Fixes #4113.
See #4110.