docs: support markdown response for AI (#5105)

docs/middleware.ts

@@ -0,0 +1,20 @@
+import { NextRequest, NextResponse } from "next/server";
+import { isMarkdownPreferred, rewritePath } from "fumadocs-core/negotiation";
+
+const { rewrite: rewriteLLM } = rewritePath("/docs/*path", "/llms.txt/*path");
+
+export function middleware(request: NextRequest) {
+	if (isMarkdownPreferred(request)) {
+		const result = rewriteLLM(request.nextUrl.pathname);
+
+		if (result) {
+			return NextResponse.rewrite(new URL(result, request.nextUrl));
+		}
+	}
+
+	return NextResponse.next();
+}
+
+export const config = {
+	matcher: "/docs/:path*",
+};