refs #276: Enable to select highlight.js style

WIP
can change custom highlight

lib/views/layout/layout.html

@@ -91,7 +91,7 @@ gh/highlightjs/cdn-release@9.12.0/build/languages/yaml.min.js
   <!-- emojione -->
   <link rel="stylesheet" href="https://cdn.jsdelivr.net/npm/emojione@3.1.2/extras/css/emojione.min.css">
   <!-- highlight.js -->
-  <link rel="stylesheet" href="https://cdn.jsdelivr.net/npm/highlight.js@9.12.0/styles/github.css">
+  <link rel="stylesheet" href="https://cdn.jsdelivr.net/npm/highlight.js@9.12.0/styles/{{ highlightType() }}.css">
 
   {% block html_additional_headers %}{% endblock %}
 

lib/views/page_presentation.html

@@ -49,7 +49,7 @@ gh/highlightjs/cdn-release@9.12.0/build/languages/yaml.min.js
     <!-- Google Fonts -->
     <link href='https://fonts.googleapis.com/css?family=Lato:400,700' rel='stylesheet' type='text/css'>
     <!-- highlight.js -->
-    <link rel="stylesheet" href="https://cdn.jsdelivr.net/npm/highlight.js@9.12.0/styles/github.css">
+    <link rel="stylesheet" href="https://cdn.jsdelivr.net/npm/highlight.js@9.12.0/styles/{{ highlightType() }}.css">
 
     <style>
       {{ customCss() }}