Add QR code preview support

QR codes can now be generated for all pages with the post processing script
the HEAD of all the html now has an open graph image tage pointing to the QR code url

layouts/partials/head.html

@@ -14,7 +14,8 @@
 <meta property="og:description" content="{{ with .Params.description }}{{ . }}{{ else }}{{ .Summary }}{{ end }}">
 <meta property="og:type" content='{{ if .IsHome }}{{ "website" }}{{ else }}{{ "article" }}{{ end }}'>
 <meta property="og:locale" content="{{ .Site.LanguageCode }}">
-<meta property="og:image" content="<page-image-url>">
+<meta property="og:url" content="{{ .Page.Permalink }}">
+<meta property="og:image" content="{{ .Page.Permalink }}qr.png">
 {{ if isset .Params "tags" }}
 <meta name="keywords" content="{{ with .Params.tags }}{{ delimit . " , " }}{{ end }}">
 {{ end -}}

post-process.sh

@@ -0,0 +1,7 @@
+#!/bin/bash
+cd public/
+
+find -name *.html | while read FILE; do
+    URL="$(grep -oP '(?<="og:url" content=")(.*)(?=")' $FILE)"
+    qrencode $URL -o $(dirname $FILE)/qr.png
+done