packages/usa-in-page-navigation/src/test/in-page-navigation-custom-content.template.html
<div class="usa-in-page-nav-container">
<aside class="usa-in-page-nav"
data-main-content-selector="#custom-main-content-region">
</aside>
<main>
<div id="custom-main-content-region">
<h3>Header in content region</h3>
</div>
<h3>Header not in content region</h3>
</main>
</div>