message: docs(client): add link and cleanup example for `hyper::client::conn`
diff: //! ```no_run
  //! # #[cfg(all(feature = "client", feature = "http1", feature = "runtime"))]
  //! # mod rt {
  +//! use tower::ServiceExt;
  //! use http::{Request, StatusCode};
  -//! use hyper::{client::conn::Builder, Body};
  +//! use hyper::{client::conn, Body};
  //! use tokio::net::TcpStream;
  //!
  //! #[tokio::main]
  //! async fn main() -> Result<(), Box<dyn std::error::Error>> {
  //! let target_stream = TcpStream::connect("example.com:80").await?;
  //!
  -//! let (mut request_sender, connection) = Builder::new()
  -//! .handshake::<TcpStream, Body>(target_stream)
  -//! .await?;
  +//! let (mut request_sender, connection) = conn::handshake(target_stream).await?;
  //!
  //! // spawn a task to poll the connection and drive the HTTP state
  //! tokio::spawn(async move {
  //! .header("Host", "example.com")
  //! .method("GET")
  //! .body(Body::from(""))?;
  +//! let response = request_sender.send_request(request).await?;
  +//! assert!(response.status() == StatusCode::OK);
  //!
  +//! // To send via the same connection again, it may not work as it may not be ready,
  +//! // so we have to wait until the request_sender becomes ready.
  +//! request_sender.ready().await?;
  +//! let request = Request::builder()
  +//! .header("Host", "example.com")
  +//! .method("GET")
  +//! .body(Body::from(""))?;
  //! let response = request_sender.send_request(request).await?;
  //! assert!(response.status() == StatusCode::OK);
  //! Ok(())
  @@ -109,6 +117,7 @@ pin_project! {
  /// Returns a handshake future over some IO.
  ///
  /// This is a shortcut for `Builder::new().handshake(io)`.
  +/// See [`client::conn`](crate::client::conn) for more.
  pub async fn handshake<T>(
  io: T,
  ) -> crate::Result<(SendRequest<crate::Body>, Connection<T, crate::Body>)>
  @@ -803,6 +812,10 @@ impl Builder {
  }
  /// Constructs a connection with the configured options and IO.
  + /// See [`client::conn`](crate::client::conn) for more.
  + ///
  + /// Note, if [`Connection`] is not `await`-ed, [`SendRequest`] will
  + /// do nothing.
  pub fn handshake<T, B>(
  &self,
  io: T,
  