added spinner to advanced search

styles/sass/welshgov/_application.scss

@@ -402,11 +402,11 @@ a.longLinkBreak {
     font-size: 19px;
 }
 
-.at-nav h3 {
-}
+// .at-nav h3 {
+// }
 
-.at-nav__chapter {
-}
+// .at-nav__chapter {
+// }
 
 .at-nav__section {
     cursor: pointer;
@@ -1107,3 +1107,16 @@ ul#sharePageLinks.active {
 .react-autosuggest__suggestion--highlighted {
     background-color: #c3c3c3;
 }
+
+/// loading spinner
+
+._loading_overlay_wrapper {
+    &._loading_overlay_wrapper--active {
+        min-height: 100%;
+        width: 100%;
+        position: fixed;
+        top: 0;
+        left: 0;
+        z-index: 99;
+    }
+}