Fixup to e3b2201: use that_detached to open browser

`open::that` can block, for example when `firefox` is the default browser
on Linux and no instance of `firefox` is running.

examples/poem/local-server-with-browser/src/main.rs

@@ -46,7 +46,10 @@ async fn main() -> Result<(), std::io::Error> {
     eprintln!("Listening at {hostname}:{port}.");
     let http_address = format!("http://{hostname}:{port}/");
     eprint!("Trying to launch a browser at {http_address}...");
-    match open::that(&http_address) {
+    // Using `open::that_detached` so that launching a new instance of firefox
+    // on Linux (for example) does not block. You can alternatively consider
+    // using `tokio::spawn_blocking` or the https://docs.rs/webbrowser/ crate.
+    match open::that_detached(&http_address) {
         Ok(()) => eprintln!(" Success!"),
         Err(err) => eprintln!("\nFailed to launch a browser: {err}"),
     }