Render internal links as relative links.

There were some locations where the site was linking to the listing
of plugin tags with an absolute ("/plugin/tags") path.  This fixes
those to render as relative paths.
This matches the rendering of all other internal links on the site,
and avoids broken links when deploying to sites rooted under a path
prefix (e.g. https://lektor.github.io/lektor-website/.)

templates/plugin-tag.html

@@ -29,5 +29,7 @@
     {{ render_plugin_list(this.items) }}
   </div>
 
-  <p>View a list of all Lektor plugin tags <a href="/plugins/tags" class="ref">here</a>.</p>
+  <p>View a list of all Lektor plugin tags
+    <a href="{{ '/plugins/tags'|url }}" class="ref">here</a>.
+  </p>
 {% endblock %}

templates/plugin.html

@@ -68,7 +68,9 @@
         {% else %}
           <p>Plugin has no tags.</p>
         {% endif %}
-        <p>View <a href="/plugins/tags" class="ref">all tags</a>.</p>
+        <p>
+          View <a href="{{ '/plugins/tags'|url }}" class="ref">all tags</a>.
+        </p>
       </div>
 
       <div class="col-sm-9 doc-styling">

templates/plugins.html

@@ -26,6 +26,7 @@
   <p>
     Plugins are also tagged with keywords and topics.
     Their tags are listed on their page and are navigable.
-    You can view a list of all of the tags <a href="/plugins/tags" class="ref">here</a>.
+    You can view a list of all of the tags
+    <a href="{{ '/plugins/tags'|url }}" class="ref">here</a>.
   </p>
 {% endblock %}