fix(website): style for bk image (#1694)

Author: hustcc

site/pages/index.less

@@ -1,3 +1,17 @@
 div[class^='PlayGround-module--exampleContainerWrapper'] {
   overflow: hidden;
-}
+}
+
+@media (max-width: 480px) {
+  .teaser-img img {
+    margin-left: 0!important;
+    margin-top: 60px!important;
+  }
+}
+
+@media (max-width: 900px) {
+  .teaser-img img {
+    margin-left: 0!important;
+    margin-top: 0!important;
+  }
+}