v1.2.0

A major new feature release, see release announcement.

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

  // old (still supported)
  $stream = new ReadableResourceStream($resource, $loop);
  $stream = new WritabeResourceStream($resource, $loop);
  $stream = new DuplexResourceStream($resource, $loop);
  
  // new (using default loop)
  $stream = new ReadableResourceStream($resource);
  $stream = new WritabeResourceStream($resource);
  $stream = new DuplexResourceStream($resource);

• 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.
  (#153, #156 and #157 by @SimonFrings and #154 by @WyriHaximus)