center notification

styles.css

@@ -7,8 +7,10 @@
 }
 
 .shiny-notification {
+  position: fixed;
   top: calc(0%);
-  padding: 0 0;
+  left: calc(50% - 200px);
+  padding: 10px 10px;
   width: 200px;
   background-color: rgba(182, 186, 191);
 }