Fix CSS style for site closure notice

Author: takezoe

_sass/_base.scss

@@ -209,4 +209,8 @@ pre {
 
 .distributed {
     color: red !important;
+}
+
+.warning {
+    font-weight: bold;
 }

index.html

@@ -6,11 +6,11 @@
 
   <h1 class="page-heading">This is the community site for all the public <a href="https://github.com/gitbucket/gitbucket">GitBucket</a> plugins.</h1>
 
-  <strong>
+  <div class="warning">
     Note: This site is no longer maintained and will soon be deleted completely.
-    The list of community plugins is now managed on a Wiki page in the gitbucket repository.<br/>
+    The list of community plugins is now managed on a Wiki page in the gitbucket repository: 
     <a href="https://github.com/gitbucket/gitbucket/wiki/Community-Plugins">https://github.com/gitbucket/gitbucket/wiki/Community-Plugins</a>
-  </strong>
+  </div>
 
   <h1 class="page-heading">Available Plugins:</h1>
   <p class="separator"/>