Changes from 2.19.0 to 2.19.1

• New blosc2_error_string() public function for getting the error string
  corresponding to a given error code. This is useful for debugging purposes.
  Thanks to Barak Ugav (@barakugav).
• Support BLOSC2_ERROR_TUNER in print_error. Thanks to Barak Ugav (@barakugav).
• Eagerly register io_cb's to avoid race. Thanks to Tom Birch (@tom-neara).