Analytics

Analytics scripts might not be as useful as you think, as most ad blocker extensions now prevent them from working, potentially limiting your data to only a small subset of your visitors.
There are many available analytics services, the most well-known being Google Analytics. They each work slightly differently, but they all should have a way to obtain a snippet of code that you can paste into the pages that you want to track.
The snippet will generally look something like this, a minimal <script> tag with an ID unique to you:
<script async src="https://www.googletagmanager.com/gtag/js?id=UA-XXXXXXXX-X"></script>
<script>
window.dataLayer = window.dataLayer || [];
function gtag(){dataLayer.push(arguments);}
gtag('js', new Date());
gtag('config', 'UA-XXXXXXXX-X');
</script>
Once you've found this code snippet for your analytics service, paste it into /_includes/analytics.html to include it on every page on your site.