v1.7.0

A major new feature release, see release announcement.

• Feature: Simplify usage by supporting new default loop.
  (#46 by @clue)

  // old (still supported)
  $promise = timeout($promise, $time, $loop);
  $promise = resolve($time, $loop);
  $promise = reject($time, $loop);
  
  // new (using default loop)
  $promise = timeout($promise, $time);
  $promise = resolve($time);
  $promise = reject($time);

• Improve test suite, use GitHub actions for continuous integration (CI),
  update PHPUnit config, run tests on PHP 8 and add full core team to the license.
  (#43 by @WyriHaximus, #44 and #45 by @SimonFrings)