_layouts/default.html

<!doctype html>
<html lang="en">
  <head>
    <meta name="viewport" content="width=device-width, initial-scale=1">
    <link rel="shortcut icon" type="image/x-icon" href="{{'/assets/images/favicon.png' | prepend: site.baseurl}}">
    <link rel="stylesheet" href="{{'/assets/bootstrap-4.1.3-dist/css/bootstrap.min.css' | prepend: site.baseurl}}">
    <link rel="stylesheet" href="{{'/assets/syntax.css' | prepend: site.baseurl}}">
    <link rel="stylesheet" href="{{'/assets/main.css' | prepend: site.baseurl}}">
    <link rel="stylesheet" href="https://cdnjs.cloudflare.com/ajax/libs/font-awesome/4.7.0/css/font-awesome.min.css">
    <script src="https://ajax.googleapis.com/ajax/libs/jquery/3.4.0/jquery.min.js"></script>
    <link href="https://fonts.googleapis.com/css?family=Work+Sans&display=swap" rel="stylesheet">
    <script src="{{ site.baseurl }}/assets/nav.js"></script>

    <title>{{ page.title }}</title>
  </head>
  <body class={{page.body_class}}>
    {% include header.html %}
    {{ content }}
    {% include footer.html %}
  </body>
</html>