Describe and Waypoint Main Menu via Signpost Heading

[jkva]

This PR addresses the following item from PAC's "ARIA-AT App Screen Reader Accessibility Observations" document:

The navigation bar items ("Test Reports", " Test Queue", etc.) are not marked up inside an unordered list to convey their grouped nature to screen reader users. They are also not preceded by a heading, either visible or off-screen/screen-reader-only.

The "The navigation bar items ("Test Reports", " Test Queue", etc.) are not marked up inside an unordered list to convey their grouped nature to screen reader users" has previously been addressed.

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Effective changes:

• A visually hidden h2 element containing "Main Menu" was added to precede the main menu nav; and
• the main menu nav is described by this h2.

[jscholes]

@jkva Looks good. A few things:

1. Can we change "Main Menu" to "Main Navigation"?
2. Exchange aria-labelledby on the nav for aria-label="Main", to avoid duplicate "navigation" announcements.
3. Move the <h2> inside the nav.
4. If not already done, add aria-labelledby to the actual list wrapping the nav links, with aria-labelledby referencing the new heading.

[isaacdurazo]

@jkva I noticed a couple of things here about the UI:

1. The Home link now reads "HOME" instead of "ARIA-AT"
2. When any link in the main nav is clicked, the "Skip to main content" button gets displayed. Is this intentional?

[jkva]

@jkva I noticed a couple of things here about the UI:

1. The Home link now reads "HOME" instead of "ARIA-AT"
2. When any link in the main nav is clicked, the "Skip to main content" button gets displayed. Is this intentional?

Hmm, neither of these things are proper. I've locally rebased this PR on #367, which overlaps with this (#366) PR in the sense that it also addresses navigation and styling.

Once #367 gets merged I'll rebase #366 on main and force push to this branch, that should put things in their proper place.

cc @alflennik @jscholes