Support for auto `<a>` generation for internal links.

[SteveLLamb]

As noted in PR SMPTE/ag-06#12, support is needed for internal links.

Example from this PR (line 160-161 of main.html):

<li><cite id="element-smpte-ag-06a">SMPTE AG-06a</cite>:2022-12-06, New Project Form
        <a>element/AG-06a-New-Project Form-2022-12-06.docx</a></li>