Converting from sass to nested vanilla css with layers (#147)

assets/css/components/_hidden.css

@@ -0,0 +1,28 @@
+/* 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. */
+
+@layer components {
+  .hidden {
+    display: none;
+  }
+
+  .js-hidden {
+    html.js & {
+      display: none;
+    }
+  }
+
+  .nojs-hidden {
+    html.nojs & {
+      display: none;
+    }
+  }
+}