fixes page size changer doesn't show up on mobile mode

Author: utchoang

ui/src/style/vars.less

@@ -239,4 +239,10 @@ a {
   .custom-icon path {
     color: @primary-color;
   }
+}
+
+@media only screen and (max-width: 576px) {
+  .ant-pagination-options {
+    display: inline-block;
+  }
 }