hacker-gh-pages-theme/_includes/head-custom.html

<!-- start custom head snippets, customize with your own _includes/head-custom.html file -->

<!-- Setup theme-color. -->
{% include head-custom-theme-colors.html %}

<!-- You can set your favicon here. -->
<!-- link rel="shortcut icon" type="image/x-icon" href="{{ '/favicon.ico' | relative_url }}" -->

<!-- end custom head snippets -->