Add support for psr/http-message v2

Author: GrahamCampbell

composer.json

@@ -23,7 +23,7 @@
         "php-http/message-factory": "^1.0",
         "psr/http-client": "^1.0",
         "psr/http-factory": "^1.0",
-        "psr/http-message": "^1.0",
+        "psr/http-message": "^1.0 || ^2.0",
         "symfony/polyfill-php80": "^1.17"
     },
     "provide": {