Update frontpage.html

Author: astonzhang

build/frontpage.html

@@ -34,7 +34,7 @@ <h3>公告</h3>
       <a href="http://product.dangdang.com/27871474.html">当当</a>、
       <a href="https://detail.tmall.com/item.htm?id=594658766444">天猫</a>
       购买黑白平装版。
-      [<a href="https://i.imgur.com/J7zXyZJ.png">新书榜</a>]
+      [<a href="https://raw.githubusercontent.com/d2l-ai/d2l-zh/master/img/frontpage/jd-190715-zh.png">新书榜</a>]
       [<a href="https://zhuanlan.zhihu.com/p/66689123">关于样书</a>]
     </li>
     <li><b>【免费资源】</b>