Lower PHP requirement to ^8.0, update CI matrix

Author: jszobody

.github/workflows/tests.yml

@@ -12,7 +12,7 @@ jobs:
 
     strategy:
       matrix:
-        php: ['8.3', '8.4', '8.5']
+        php: ['8.0', '8.3', '8.5']
 
     name: PHP ${{ matrix.php }}
 

composer.json

@@ -22,7 +22,7 @@
     }
   ],
   "require": {
-    "php": "^8.3",
+    "php": "^8.0",
     "ext-dom": "*"
   },
   "require-dev": {