Allow psr/http-message v2

Author: GrahamCampbell

composer.json

@@ -12,7 +12,7 @@
     ],
     "require": {
         "php": "^7.1 || ^8.0",
-        "psr/http-message": "^1.0",
+        "psr/http-message": "^1.0 || ^2.0",
         "psr/http-factory": "^1.0",
         "php-http/message-factory": "^1.0.2",
         "php-http/discovery": "^1.7"