Fix including style.css in head.html (#173)

Author: gomzyakov

_includes/head.html

@@ -12,7 +12,7 @@
           integrity="sha384-GLhlTQ8iRABdZLl6O3oVMWSktQOp6b7In1Zl3/Jr59b6EGGoI1aFkw7cmDA6j6gD"
           crossorigin="anonymous">
     <link rel="stylesheet" href="https://cdn.jsdelivr.net/npm/[email protected]/font/bootstrap-icons.css">
-    <link rel="stylesheet" href="/assets/style.css">
+    <link rel="stylesheet" href="{{ site.url }}/assets/style.css">
 
     <!-- Favicons -->
     <link rel="icon" href="{{ site.url }}/assets/favicon/favicon.ico">