AC-1615: Add PHP8 support to magento/composer-root-update-plugin

Author: Stanislav Idolov

src/Magento/ComposerRootUpdatePlugin/composer.json

@@ -8,7 +8,7 @@
     "AFL-3.0"
   ],
   "require": {
-    "php": "~7.3.0||~7.4.0",
+    "php": "~7.3.0||~7.4.0||~8.0.0||~8.1.0",
     "composer/composer": "^1.0 || ^2.0",
     "composer-plugin-api": "^1.0 || ^2.0"
   },