Update NavDropDownButton caret to white

Author: jaygiang

templates/react-javascript/src/index.css

@@ -19,4 +19,10 @@ code {
 html,
 body {
   width: 100%;
+}
+
+@media (min-width: 64em) {
+  .usa-nav__primary button[aria-expanded=false] span:after {
+      background: white;
+  }
 }