Add cache buster

docs/_includes/head.html

@@ -16,7 +16,7 @@
   {% if page.mdi %}
     <link rel="stylesheet" href="{{ site.mdi }}">
   {% endif %}
-  <link rel="stylesheet" href="{{ site.url }}/css/bulma-docs.css">
+  <link rel="stylesheet" href="{{ site.url }}/css/bulma-docs.css?v={{ site.time | date: "%Y%m%d-%H%M" }}">
 
   <link rel="canonical" href="{{ page.url | replace:'index.html','' | prepend: site.url }}">
   <link rel="alternate" type="application/rss+xml" title="{{ site.title }}" href="{{ "/feed.xml" | prepend: site.url }}">