fix render issue

src/App.js

@@ -1,7 +1,27 @@
 import React from "react";
+import { BrowserRouter as Router, Route, Routes } from "react-router-dom";
+import MainNavigation from "./components/MainNavigation";
+import SideNavigation from "./components/SideNavigation";
+import MarkdownContent from "./components/MarkdownContent";
+import "./App.css";
 
 const App = () => {
-    return <h1>Welcome to My React Project</h1>;
+    return (
+        <Router>
+            <div className="app-container">
+                <MainNavigation />
+                <div className="content-container">
+                    <SideNavigation />
+                    <main className="main-content">
+                        <Routes>
+                            <Route path="/" element={<h1>Welcome to My React Project</h1>} />
+                            <Route path="/markdown/:id" element={<MarkdownContent />} />
+                        </Routes>
+                    </main>
+                </div>
+            </div>
+        </Router>
+    );
 };
 
 export default App;