Adopt WAI-ARIA guidance for breadcrumbs

[joewiz]

See https://www.w3.org/TR/wai-aria-practices-1.1/#breadcrumb and https://www.w3.org/TR/wai-aria-practices-1.1/examples/breadcrumb/index.html.

Currently pages like https://history.state.gov/historicaldocuments use the following breadcrumb markup:

<div class="hsg-breadcrumb-wrapper">
    <ol class="breadcrumb">
        <li>
            <a href="">Home</a>
        </li>
        <li>
            <a href="/historicaldocuments">Historical Documents</a>
        </li>
    </ol>
</div>

The guidelines suggest the use of (1) <nav aria-label="Breadcrumb" class="breadcrumb"> and (2) aria-current="page" for the current page. Thus the markup should be as follows (I assume a wrapper div around the <nav> would probably be okay, if necessary):

<nav aria-label="Breadcrumb" class="breadcrumb">
    <ol>
        <li>
            <a href="">Home</a>
        </li>
        <li>
            <a href="/historicaldocuments" aria-current="page">Historical Documents</a>
        </li>
    </ol>
</nav>