feat: 中间页背景更换

src/pages/middlePageNew/middlePageNew.less

@@ -26,7 +26,7 @@
     position: absolute;
     top: calc(50% - 1624px/2);
     left: 0;
-    .sparkBg("mid/bg.jpg");
+    .sparkBg("mid/bg.png");
     .btn {
       width: 750px;
       height: 1624px;