build: allow installation of psr/http-message version 2

Resolves: #41

Author: JaZo

composer.json

@@ -27,7 +27,7 @@
         "php-http/discovery": "^1.14",
         "php-http/mock-client": "^1.5",
         "psr/http-factory": "^1.0",
-        "psr/http-message": "^1.0",
+        "psr/http-message": "^1.0|^2.0",
         "symfony/string": "^5.4|^6.0"
     },
     "require-dev": {