beautifulSA-jekyll/_includes/ext-css.html

{% if include.css.sri %}
  <link href="{{ include.css.href }}" rel="stylesheet" integrity="{{ include.css.sri }}" crossorigin="anonymous">
{% elsif include.css.href %}
  <link rel="stylesheet" href="{{ include.css.href }}" />
{% else %}
  <link rel="stylesheet" href="{{ include.css }}" />
{% endif %}