#115 add route for welcome page

apps/doi-landing-page/src/landingPage/WelcomeLandingPage.tsx

+export function WelcomeLandingPage() {
+  return <p>Welcome</p>;
+}

apps/doi-landing-page/src/routes.tsx

 import { DOI_PREFIX_PARAM, DOI_SUFFIX_PARAM } from 'hooks/path';
 import { LandingPage } from 'landingPage/LandingPage';
+import { WelcomeLandingPage } from 'landingPage/WelcomeLandingPage';
 import type { RouteObject } from 'react-router-dom';
 import { PageNotFound } from 'routing/PageNotFound';
 
@@ -8,10 +9,19 @@ const DOI_ROUTE = {
   element: <LandingPage />,
 };
 
+const WELCOME_ROUTE = {
+  path: '',
+  element: <WelcomeLandingPage />,
+};
+
 export const routes: RouteObject[] = [
+  {
+    path: '/',
+    element: <WelcomeLandingPage />,
+  },
   {
     path: 'doi',
-    children: [DOI_ROUTE],
+    children: [WELCOME_ROUTE, DOI_ROUTE],
   },
   DOI_ROUTE,
   {