center notification

styles.css

@@ -9,7 +9,7 @@
 .shiny-notification {
   position: fixed;
   top: calc(0%);
-  left: calc(50% - 200px);
+  left: calc(50%);
   padding: 10px 10px;
   width: 200px;
   background-color: rgba(182, 186, 191);