Merge pull request #1 from lafourchette/feature/php8

PHP 8 compatibility

Author: yoanmLf

composer.json

@@ -16,8 +16,8 @@
         "php": ">=5.4",
         "psr/http-message": "^1.0",
         "php-http/client-implementation": "^1.0",
-        "php-http/client-common": "^1.0",
-        "php-http/httplug": "^1.0",
+        "php-http/client-common": "^1.0|^2.0",
+        "php-http/httplug": "^1.0|^2.0",
         "php-http/message-factory": "^1.0",
         "php-http/discovery": "^1.0"
     },