Inprove accessibility of paragraphs administration : add h3 around title

Problem/Motivation

In Drupal back office, paragraphs edit forms can't be identified by screen readers in "Paragraph (stable)" field widget plugin. This issue complicates the contribution work of visually impaired people.

Steps to reproduce

For example, this issue can be observed using NVDA : https://www.nvaccess.org/
This software generate a quick access summary from the struture (headers) of a web page (h1, h2, h3, etc.)

ex:

<div class="paragraph-type js-form-wrapper form-wrapper" data-drupal-selector="edit-field-contenu-principal-0-top-type" id="edit-field-contenu-principal-0-top-type--Jsmyx_3d7nk">
<span class="paragraph-type-label">Some paragraph name</span>
</div>

Proposed resolution

Add h3 header markup around the paragraph name so that it is integrated to the structure of the administration page in the back office.

ex:

<div class="paragraph-type js-form-wrapper form-wrapper" data-drupal-selector="edit-field-contenu-principal-0-top-type" id="edit-field-contenu-principal-0-top-type--Jsmyx_3d7nk">
<h3><span class="paragraph-type-label">Some paragraph name</span></h3>
</div>