python-chess v0.27.3

Changes:

* `XBoardProtocol` will no longer raise an exception when the engine resigned.
  Instead it sets a new flag `PlayResult.resigned`. `resigned` and
  `draw_offered` are keyword-only arguments.
* Renamed `chess.pgn.{Game,Header,Board}Creator` to
  `{Game,Headers,Board}Builder`. Aliases kept in place.

Bugfixes:

* Make `XBoardProtocol` robust against engines that send a move after claiming
  a draw or resigning. Thanks @pascalgeo.
* `XBoardProtocol` no longer ignores `Hint:` sent by the engine.
* Fix handling of illegal moves in `XBoardProtocol`.
* Fix exception when engine is shut down while pondering.
* Fix unhandled internal exception and file descriptor leak when engine
  initialization fails.
* Fix `HordeBoard.status()` when black pieces are on the first rank.
  Thanks @Wisling.

New features:

* Added `chess.pgn.Game.builder()`, `chess.pgn.Headers.builder()` and
  `chess.pgn.GameNode.dangling_node()` to simplify subclassing `GameNode`.
* `EngineProtocol.communicate()` is now also available in the synchronous API.