Moving sass and js files in to the assets directory.

assets/sass/components/hidden/_hidden.scss

@@ -0,0 +1,29 @@
+// Hidden
+//
+// Hide elements from all users. Compare to the visually-hidden component.
+//
+// Used for elements which should not be immediately displayed to any user. An
+// example would be a collapsible fieldset that will be expanded with a click
+// from a user.
+//
+// For anything you want to hide on page load when JavaScript is enabled, use
+// the `.js-hidden` class.
+
+.hidden,
+%hidden {
+  display: none;
+}
+
+.js-hidden,
+%js-hidden {
+  html.js & {
+    @extend %hidden;
+  }
+}
+
+.nojs-hidden,
+%nojs-hidden {
+  html.nojs & {
+    @extend %hidden;
+  }
+}