expose on_connect v2 (#1754)

Co-authored-by: Mikail Bagishov <bagishov.mikail@yandex.ru>

actix-http/src/helpers.rs

@@ -50,6 +50,7 @@ impl<'a> io::Write for Writer<'a> {
         self.0.extend_from_slice(buf);
         Ok(buf.len())
     }
+
     fn flush(&mut self) -> io::Result<()> {
         Ok(())
     }