Support `categories` parameter for posts (#73)

layouts/partials/article_metadata.html

@@ -8,13 +8,26 @@
     </time>
   </span>
 
+  {{ if isset $.Params "categories" }}
+  {{ $categoriesLen := len $.Params.categories }}
+  {{ if gt $categoriesLen 0 }}
+  <span class="article-categories">
+    <i class="fa fa-folder"></i>
+    {{ range $k, $v := $.Params.categories }}
+    <a href="{{ "/categories/" | relLangURL }}{{ . | urlize | lower }}">{{ . }}</a
+    >{{ if lt $k (sub $categoriesLen 1) }}, {{ end }}
+    {{ end }}
+  </span>
+  {{ end }}
+  {{ end }}
+
   {{ if isset $.Params "tags" }}
   {{ $tagsLen := len $.Params.tags }}
   {{ if gt $tagsLen 0 }}
   <span class="article-tags">
     <i class="fa fa-tags"></i>
     {{ range $k, $v := $.Params.tags }}
-    <a class="article-tag-link" href="{{ $.Site.BaseURL }}tags/{{ . | urlize | lower }}">{{ . }}</a
+    <a href="{{ "/tags/" | relLangURL }}{{ . | urlize | lower }}">{{ . }}</a
     >{{ if lt $k (sub $tagsLen 1) }}, {{ end }}
     {{ end }}
   </span>

static/css/hugo-academic.css

@@ -403,6 +403,7 @@ article {
 }
 
 .article-metadata .article-date,
+.article-metadata .article-categories,
 .article-metadata .article-tags {
   margin-right: 10px;
 }