Canonical URLs should be absolute not relative (#66)

https://developers.google.com/search/docs/advanced/crawling/consolidate-duplicate-urls#rel-canonical-link-method

layouts/partials/head.html

@@ -4,7 +4,7 @@
   <meta http-equiv="X-UA-Compatible" content="IE=edge">
 
   {{ hugo.Generator }}
-  <link rel="canonical" href="{{ .RelPermalink }}">
+  <link rel="canonical" href="{{ .Permalink }}" />
 
   {{ if .IsHome }}
     {{ with .Site.Params.homeMetaContent }}