message: docs(example): fix http_proxy to use upgrades
diff: @@ -32,6 +32,7 @@ async fn main() -> Result<(), Box<dyn std::error::Error>> {
  .http1_preserve_header_case(true)
  .http1_title_case_headers(true)
  .serve_connection(stream, service_fn(proxy))
  + .with_upgrades()
  .await
  {
  println!("Failed to serve connection: {:?}", err);
  