Resolve "ci: build fail"

Closes #13 (closed)

src/pages/dummy_page.js

+import React from "react";
+import Layout from "@theme/Layout";
+
+function Dummy() {
+  return (
+    <Layout title="Bonjour">
+      <div
+        style={{
+          display: "flex",
+          justifyContent: "center",
+          alignItems: "center",
+          height: "50vh",
+          fontSize: "20px",
+        }}>
+        <p>
+          Editez <code>pages/dummy.js</code> et sauvegardez pour recharger.
+        </p>
+      </div>
+    </Layout>
+  );
+}
+
+export default Dummy;