Refactored collections store and layout components

frontend/utils/routeHelpers.js

@@ -1,14 +1,18 @@
 // @flow
 
-export function homeUrl() {
+export function homeUrl(): string {
   return '/dashboard';
 }
 
-export function newCollectionUrl() {
+export function newCollectionUrl(): string {
   return '/collections/new';
 }
 
-export function searchUrl(query: string) {
+export function searchUrl(query: string): string {
   if (query) return `/search/${query}`;
   return `/search`;
 }
+
+export function notFoundUrl(): string {
+  return '/404';
+}