[Accessibility]: Accessibility issues Tracking (Phase 1)

Describe the accessibility issue A clear and concise description of what the accessibility is.

Lighthouse report surfaced the following issues:

Can't fix (quarto issue):

[ ] Search button in nav bar: Inaccessible button name. Quarto issue: https://github.com/quarto-dev/quarto-cli/issues/678

[ ] Callouts: div.callout-header.d-flex.align-content-center Quarto issue: https://github.com/quarto-dev/quarto-cli/issues/4934

[aria-*] attributes do not match their roles
Each ARIA role supports a specific subset of aria-* attributes. Mismatching these invalidates the aria-* attributes. 
[Learn how to match ARIA attributes to their roles](https://dequeuniversity.com/rules/axe/4.8/aria-allowed-attr).

Can fix:

[x] Footer logos (posit guide and posit logo): Lacking alt text (#56)
[x] Nav bar text: contrast between font color and background (contrast is too low) (#56)
[x] [aria-hidden="true"] elements contain focusable descendants (I think that this is an issue for both the website logo and the menu item drop-down in the nav - I have fixed the menu item issue) (#56)

Focusable descendents within an [aria-hidden="true"] element prevent those interactive elements from being available to users of assistive technologies like screen readers. Learn how aria-hidden affects focusable elements.

Uncategorized - unsure if we can fix

[ ] [aria-hidden="true"] elements contain focusable descendants (Quarto team thinks that this is resolved in v1.5 so I can verify at a later date - however, the Quarto website doesn't have this issue so I am assuming that v1.5 does in fact resolve this issue)

Focusable descendents within an [aria-hidden="true"] element prevent those interactive elements from being available to users of assistive technologies like screen readers. Learn how aria-hidden affects focusable elements.
```
<body class="nav-fixed quarto-light" data-tabster="{&quot;root&quot;:{}}" data-new-gr-c-s-check-loaded="14.1169.0" 
data-gr-ext-installed="" data-bs-offset="81" style="padding-top: 81px;">
```
[ ] [aria-*] attributes do not match their roles

(Fix?: https://github.com/quarto-dev/quarto-cli/pull/9553/files)

Resolution If applicable, add the solution to resolve this accessibility issue.

Additional context Add any other context about the problem here.

posit-dev / product-doc-theme

[Accessibility]: Accessibility issues Tracking (Phase 1) #55