feat: add react-syntax-highlighter and update JSDoc cheatsheet layout

Integrate react-syntax-highlighter for improved code example rendering and enhance the JSDoc cheatsheet layout with a new navigation structure and quick reference section.

components/Header.tsx

@@ -0,0 +1,19 @@
+"use client"
+
+import { BookOpen } from "lucide-react"
+import Link from "next/link"
+
+export default function Header() {
+  return (
+    <header className="border-b border-border bg-card/50 backdrop-blur-sm sticky top-0 z-50">
+      <div className="w-full px-6 py-4">
+        <div className="flex items-center">
+          <Link href="/" className="flex items-center gap-2">
+            <BookOpen className="h-6 w-6 text-primary" />
+            <h1 className="text-2xl font-bold text-foreground">JSDoc Cheatsheet</h1>
+          </Link>
+        </div>
+      </div>
+    </header>
+  )
+}