v1.3.0

• Feature: Improve error reporting by appending previous exception messages.
  (#26 by @clue)

  For most common use cases this means that simply reporting the Exception
  message should give the most relevant details for any issues:

  React\Promise\Stream\buffer($stream)->then(function (string $contents) {
      // …
  }, function (Exception $e) {
      echo 'Error:' . $e->getMessage() . PHP_EOL;
  });

• Improve documentation, describe promise and stream data types.
  (#27 by @clue and #23 by @WyriHaximus)

• Improve test suite and add .gitattributes to exclude dev files from exports.
  Use GitHub actions for continuous integration (CI) and run tests on PHPUnit 9 and PHP 8.
  (#21 by @reedy and #22, #24 and #25 by @SimonFrings)