fix: show different subtitle for each i18n variant in exampleSite

exampleSite/hugo.yaml

@@ -18,20 +18,23 @@ languages:
         title: Example Site
         weight: 1
         params:
-            description: Example description
+            sidebar:
+                subtitle: Example description
     zh-cn:
         languageName: 中文
         title: 演示站点
         weight: 2
         params:
-            description: 演示说明
+            sidebar:
+                subtitle: 演示说明
     ar:
         languageName: عربي
         languagedirection: rtl
         title: موقع تجريبي
         weight: 3
         params:
-            description: وصف تجريبي
+            sidebar:
+                subtitle: وصف تجريبي
 
 services:
     # Change it to your Disqus shortname before using