Show progressbar while loading lunr and data

assets/_utils.scss

@@ -46,6 +46,15 @@
   display: none;
 }
 
+@mixin spin($duration) {
+  animation: spin $duration ease infinite;
+  @keyframes spin {
+    100% {
+      transform: rotate(360deg);
+    }
+  }
+}
+
 @mixin fixed {
   position: fixed;
   top: 0;