[PWA-2401] Support PHP 8.0 and 8.1 for all PWA related repo's (#17)

* PWA-2401 Update PHP requirements to support PHP 8.0 and 8.1

* PWA-2401 Remove 8.1 support for now

* Revert "PWA-2401 Remove 8.1 support for now"

This reverts commit b7ab1c581387ed06df7fdbafc89637f184e83ffa.

* PWA-2401 Remove 8.0 support to follow core

Author: mikhaelbois

composer.json

@@ -5,7 +5,7 @@
         "sort-packages": true
     },
     "require": {
-        "php": "~7.3.0||~7.4.0",
+        "php": "~7.4.0||~8.1.0",
         "magento/framework": "*",
         "magento/upward": "*",
         "magento/module-config": "*",