Plugin FAQ headings should use H3 tags

[jonoaldersonwp]

Plugins FAQ sections, like ​https://wordpress.org/plugins/wordpress-seo/, should use <h3> tags to mark up the 'names' of questions in the <dl> structure.

This is transformed on load using JavaScript, but should instead be correct in the HTML response.

Specifically, the markup should be altered to:

<dl>
  <dt><h3>{{Question}}</h3></dt>
  <dd>{{Answer}}</dd>
  {...}
</dl>

Note that {{answer}} typically already contains formatting (such as paragraph structures), and shouldn't therefore need changing.

[dd32]

In 9826:

Plugin Directory: FAQ: Alter the markup to be <dt><h3>{{Question}}</h3></dt> to match the Javascript FAQ implementation.

This is run on import, so it'll only affect plugins upon their next commit rather than immediately.

Fixes #5191.

[dd32]

Example: ​https://wordpress.org/plugins/eber/ (The first plugin commit when I checked that had a FAQ)

[dd32]

In 9827:

Plugin Directory: API: Update to respect the new markup format introduced in [9826].

See #5191.

[ocean90]

In 9828:

Plugin Directory, i18n import: Update to respect the new readme markup format introduced in [9826].

See #5191.