feat: artalk 支持點擊打開大圖

feat: 設置了隨系統而切換淺色和深色模式後，評論和 mermaind 也會跟隨切換顏色
feat: artalk 最新評論，從 artalk 配置讀取頭像 CDN 和默認頭像
fix: 修復代碼塊在未展開時，點擊複製按鈕，無法複製的 bug
improvement: 代碼和性能優化
improvement: artalk 獲取評論數，由 LoadCountWidget 改為 loadCountWidget

layout/includes/third-party/comments/facebook_comments.pug

@@ -22,9 +22,19 @@ script.
       ele.setAttribute('crossorigin', 'anonymous')
       ele.setAttribute('id', 'facebook-jssdk')
       document.getElementById('fb-root').insertAdjacentElement('afterbegin',ele)
-    }   
+    }
   }
 
+  function fbModeChange (theme) {
+    const $fbComment = document.getElementsByClassName('fb-comments')[0]
+    if ($fbComment && typeof FB === 'object') {
+      $fbComment.setAttribute('data-colorscheme',theme)
+      FB.XFBML.parse(document.getElementById('post-comment'))
+    }
+  }
+
+  btf.addModeChange('facebook_comments', fbModeChange)
+
   if ('!{theme.comments.use[0]}' === 'Facebook Comments' || !!{theme.comments.lazyload}) {
     if (!{theme.comments.lazyload}) btf.loadComment(document.querySelector('#post-comment .fb-comments'), loadFBComment)
     else loadFBComment()