Add colvmn to your site as a submodule:
git submodule add https://github.com/stevedekorte/colvmn.git colvmnMake each page a directory with two files. index.html is a thin shell:
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<link rel="stylesheet" href="/colvmn/style.css">
<title>My Page</title>
</head>
<body>
<div class="page"></div>
<script src="/colvmn/layout/layout.js" type="module"></script>
</body>
</html>_index.md holds the content:
---
title: My Page
topTitle: My Site
subtitle: A short tagline for the page.
---