allow guzzlehttp/psr7 v2.0 dependency (#17)

* update guzzlehttp deps

* allow both v1.6 and v2.0

Author: mhdcodes

composer.json

@@ -19,7 +19,7 @@
     "require": {
         "php": "^7.4|^8.0",
         "ext-json": "*",
-        "guzzlehttp/psr7": "^1.6",
+        "guzzlehttp/psr7": "^1.6|^2.0",
         "guzzlehttp/guzzle": "^7.0",
         "brick/money": "^0.5.2"
     },