Chapter 4 - add routers for dashboard pages

app/dashboard/customers/page.tsx

@@ -0,0 +1,3 @@
+export default function CustomersPage() {
+    return <p>Customers page</p>
+}

app/dashboard/invoices/page.tsx

@@ -0,0 +1,3 @@
+export default function InvoicesPage() {
+    return <p>Invoices page</p>
+}

app/dashboard/page.tsx

@@ -0,0 +1,3 @@
+export default function Page() {
+    return <p>Dashboard Page</p>;
+}