Add support for PHP 8.4 in PHPUnit workflow

Author: nadar

.github/workflows/phpunit.yml

@@ -10,7 +10,7 @@ jobs:
     runs-on: ubuntu-latest
     strategy:
       matrix:
-        php: ['8.1', '8.2', '8.3']
+        php: ['8.1', '8.2', '8.3', '8.4']
 
     steps:
     - name: Checkout code