_includes/head.html

<head>

  <meta charset="utf-8">
  <meta name="viewport" content="width=device-width, initial-scale=1, shrink-to-fit=no">

  <title>
    {% if page.title %}{{ page.title | escape }} - {{ site.title | escape }}
    {% else %}{{ site.title | escape }}{% endif %}
  </title>

  <meta name="description" content="{{ page.excerpt | default: site.description | strip_html | normalize_whitespace | truncate: 160 | escape }}">

  <link rel="stylesheet" href="https://maxcdn.bootstrapcdn.com/bootstrap/4.0.0-beta.2/css/bootstrap.min.css" integrity="sha384-PsH8R72JQ3SOdhVi3uxftmaW6Vc51MKb0q5P2rRUpPvrszuE4W1povHYgTpBfshb" crossorigin="anonymous">

  <link rel="stylesheet" href="https://cdnjs.cloudflare.com/ajax/libs/simple-line-icons/2.4.1/css/simple-line-icons.min.css" integrity="sha256-7O1DfUu4pybYI7uAATw34eDrgQaWGOfMV/8erfDQz/Q=" crossorigin="anonymous">

  <link rel="stylesheet" href="https://cdnjs.cloudflare.com/ajax/libs/hamburgers/0.9.1/hamburgers.min.css" integrity="sha256-hCM6SsLZUT2/Vkykg2meK/x+qOo9SJPfYif9agoSGOk=" crossorigin="anonymous">

  <link rel="stylesheet" href="{{"/assets/main.css" | relative_url }}">
  <link rel="canonical" href="{{ page.url | replace:'index.html','' | absolute_url }}">
  <link rel="alternate" type="application/rss+xml" title="{{ site.title | escape }}" href="{{ " /feed.xml" | relative_url }}">

</head>