add line for github pages to custom html

Author: danielparthier

_includes/head/custom.html

@@ -2,4 +2,5 @@
 <link rel="icon" type="image/svg+xml" href="/assets/favicon.svg" />
 <link rel="shortcut icon" href="/assets/favicon.ico" />
 <link rel="apple-touch-icon" sizes="180x180" href="/assets/apple-touch-icon.png" />
-<link rel="manifest" href="/assets/site.webmanifest" />
+<link rel="manifest" href="/assets/site.webmanifest" />
+<link rel="shortcut icon" href="{{ "/assets/favicon.ico" | relative_url }}">