docs: add drand banner image

src/theme/Layout/index.js

@@ -0,0 +1,20 @@
+import React from 'react';
+import OriginalLayout from '@theme-original/Layout';
+import useDocusaurusContext from '@docusaurus/useDocusaurusContext';
+// import styles from './styles.module.css'; // Optionally, add custom CSS
+
+export default function Layout(props) {
+  const {siteConfig} = useDocusaurusContext();
+  return (
+    <OriginalLayout {...props}>
+      {/* Add your banner image below the navbar */}
+      <div>
+        <img
+          src="/img/banner.avif"  // Path to your banner image
+          alt="Banner"
+        />
+      </div>
+      {props.children}
+    </OriginalLayout>
+  );
+}