docs: add clean markdown version of all documentation pages (#11308)

* added route to book

* added to resources

* added route to ui

* added to user guide

www/apps/user-guide/middleware.ts

@@ -0,0 +1,15 @@
+import { NextResponse } from "next/server"
+import type { NextRequest } from "next/server"
+
+export function middleware(request: NextRequest) {
+  return NextResponse.rewrite(
+    new URL(
+      `${request.nextUrl.basePath}/md-content${request.nextUrl.pathname.replace("/index.html.md", "")}`,
+      request.url
+    )
+  )
+}
+
+export const config = {
+  matcher: "/:path*/index.html.md",
+}