Implement dataset page v0.1 + Home improvements (#892)

* [examples/openspending][xl]: implement dataset page v0.1, add pagination to the datasets grid

* [examples/openspending][m] - fix build + add tests

---------

Co-authored-by: Luccas Mateus de Medeiros Gomes <luccasmmg@gmail.com>

examples/openspending/components/_shared/Layout.tsx

@@ -0,0 +1,10 @@
+import { Header } from '../Header';
+
+export default function Layout({ children }) {
+  return (
+    <div className="bg-white min-h-screen">
+      <Header />
+      {children}
+    </div>
+  );
+}