Output is a labelable element, but accname calculation for output ignores label

[dd8]

Should the accessible name computation for output include the label element?
https://w3c.github.io/html-aam/#output-element-accessible-name-computation

It's categorised as labelable in the the HTML Standard:
https://html.spec.whatwg.org/multipage/forms.html#category-label

Chrome/Edge/Opera/Firefox use the label in their accessible name calculation, and use "My label" as the name. Safari doesn't use label and uses "This is some output" as the name but maps output to AXStaticText which doesn't have a name.

<label for="test">My label</label>
<output id="test">This is some output</output>

[scottaohara]

duplicate of #225

pull request is just waiting on people to actually review it #402