Added

• Add Support for PHP 8
  This adapter can now be installed with PHP 8, even though Guzzle 6 is not tested on PHP 8. If you need a PSR-18 client, use Guzzle 7 which natively implements PSR-18. If you need the HTTPlug interfaces for asynchronous calls or for a system that still requires HTTPlug, use the guzzle7-adapter instead of this repository.

Fixed

• \Http\Adapter\Guzzle6\Client::sendRequest no longer throws any exceptions that do not implement
  the PSR exception interface.

  Instead of \UnexpectedValueException we now throw Http\Adapter\Guzzle6\Exception\UnexpectedValueException
  (which extends \UnexpectedValueException and implements Psr\Http\Client\ClientExceptionInterface).

  Instead of \RuntimeException we now throw Http\Client\Exception\TransferException
  (which extends \RuntimeException and implements Psr\Http\Client\ClientExceptionInterface).

This major release drops PHP 5.x support and implements HTTPlug 2.0/PSR-18.

• fix regression with creating the adapter without an explicit guzzle client