PHP 8 support

Author: Andrey Helldar

composer.json

@@ -15,7 +15,7 @@
         }
     ],
     "require": {
-        "php": "^7.1.3",
+        "php": "^7.1.3|^8.0",
         "ext-dom": "*",
         "ext-mbstring": "*",
         "andrey-helldar/support": "^1.16.0"