Put the checker on your own page
A documentation page about accessible colour is more useful with the checker in it. There is no account, no key and no script to load on your side — one iframe, and everything computes in your reader's browser exactly as it does here.
<iframe src="https://huecomb.com/embed/contrast" title="Contrast checker by HueComb"
width="100%" height="760" style="border:1px solid #ddd;max-width:720px" loading="lazy"></iframe>
<p><a href="https://huecomb.com/?ref=embed">Contrast checker by HueComb</a></p>