fix Exception demo

src/components/Exception/index.less

@@ -15,10 +15,12 @@
 
   .imgEle {
     height: 360px;
-    width: 430px;
+    width: 100%;
+    max-width: 430px;
     float: right;
     background-repeat: no-repeat;
     background-position: 50% 50%;
+    background-size: 100% 100%;
   }
 
   .content {