Test procedure in H71 doesn't require legend to be first child

[dd8]

The description of H71 says "The first element inside the fieldset must be a legend element" but the test procedure doesn't mention this and passes no matter where the legend is positioned:

For groups of related controls where the individual labels for each control do not provide a sufficient description, and an additional group level description is needed:
Check that the group of logically related input or select elements are contained within fieldset elements.
Check that each fieldset has a legend element that includes a description for that group.

https://www.w3.org/WAI/WCAG21/Techniques/html/H71

The HTML Standard specifies that legend must be the first element in the fieldset if present:
https://html.spec.whatwg.org/multipage/form-elements.html#the-legend-element

If the legend is the first child the fieldset is mapped to a group named "First child" in Chrome/Firefox/Safari:

  <fieldset>
      <legend>First child</legend>
      <input aria-label="Search">
  </fieldset>

If the legend is embedded in some divs, it passes the H71 test procedure, but the fieldset is mapped to an unnamed group in Chrome/Firefox/Safari:

  <fieldset>
    <div><div><legend>First non-generic element</legend></div></div>
    <input aria-label="Search">
  </fieldset>

Suggested fix - change:

Check that each fieldset has a legend element that includes a description for that group

to

Check that each fieldset has a legend element that is the first child in the fieldset and includes a description for that group

or

Check the first child in each fieldset is a legend element that includes a description for that group

[detlevhfischer]

Well spotted. I have created a PR to change this: #3096