v1.8.0

• Feature: Add new sleep() function and deprecate resolve() and reject() functions.
  (#51 by @clue)

  // deprecated
  React\Promise\Timer\resolve($time);
  React\Promise\Timer\reject($time);
  
  // new
  React\Promise\Timer\sleep($time);

• Feature: Support PHP 8.1 release.
  (#50 by @Thomas-Gelf, #52 by @clue and #48 by @SimonFrings)

• Improve API documentation and add parameter types and return types.
  (#49 by @clue and #47 by @SimonFrings)