chore: set PHP platform version to 8.1 in composer.json

Author: bbsnly

composer.json

@@ -47,6 +47,9 @@
     },
     "config": {
         "optimize-autoloader": true,
+        "platform": {
+            "php": "8.1"
+        },
         "preferred-install": "dist",
         "sort-packages": true
     }