basic not-found page

client/src/AppRouter.tsx

@@ -12,6 +12,7 @@ import {
   currentUserSubPath,
 } from "./models/paths";
 import { BooksLayout } from "./pages/books/BooksLayout";
+import { NotFound } from "./pages/NotFound";
 
 export function AppRouter() {
   return (
@@ -51,6 +52,7 @@ export function AppRouter() {
             key="user"
             element={<CurrentUserShow />}
           />
+          <Route path="*" key="notFound" element={<NotFound />} />
         </Route>
       </Routes>
     </BrowserRouter>

client/src/pages/NotFound.tsx

@@ -0,0 +1,13 @@
+import { Link } from "react-router-dom";
+import { rootPath } from "../models/paths";
+
+export function NotFound() {
+  return (
+    <div>
+      <p>The page at this address was not found.</p>
+      <p>
+        <Link to={rootPath}>Return to main page</Link>
+      </p>
+    </div>
+  );
+}