Ask this site for Jekyll

Make an include with both lines, then use it on any page or layout.

_includes/askthissite.html

<div data-everypage-site="YOUR-SITE-ID"></div>
<script src="https://askthissite.com/embed.js" async></script>

Any page or layout

{% include askthissite.html %}

Your site id is on your site's page after you sign up.