spell 'stream' correctly

Thanks @bobrik.

README.rst

@@ -142,7 +142,7 @@ be ready for sending or receiving application data:
 .. code-block:: rust
 
    if conn.is_established() {
-       // Handshake completed, send some data on steadm 0.
+       // Handshake completed, send some data on stream 0.
        conn.stream_send(0, b"hello", true);
    }
 

src/lib.rs

@@ -157,7 +157,7 @@
 //! # let scid: [u8; 16] = [0xba; 16];
 //! # let mut conn = quiche::accept(&scid, None, &mut config).unwrap();
 //! if conn.is_established() {
-//!     // Handshake completed, send some data on steadm 0.
+//!     // Handshake completed, send some data on stream 0.
 //!     conn.stream_send(0, b"hello", true);
 //! }
 //! ```