created base structure of admin page

app/admin/page.tsx

@@ -0,0 +1,10 @@
+import React from "react";
+
+export default function AdminPage() {
+  return (
+    <div>
+      <h1>AdminPage to manage explainegy</h1>
+      <a href="/admin/articles/">articles</a> <a href="/admin/categories/">categories</a> <br />
+    </div>
+  );
+}