Add Guzzle 7 support

Author: Lucas P. Pons

composer.json

@@ -18,7 +18,7 @@
     "minimum-stability": "stable",
     "require": {
         "php": ">=7.2",
-        "guzzlehttp/guzzle": "^6.2",
+        "guzzlehttp/guzzle": "^6.2|^7.2",
         "illuminate/http": "^7.0",
         "illuminate/support": "^7.0",
         "nesbot/carbon": "^2.0",