add php 8.4 to phpunit.yml

Author: dozsan

.github/workflows/phpunit.yml

@@ -15,7 +15,7 @@ jobs:
         strategy:
             fail-fast: false
             matrix:
-                php: ['8.1', '8.2', '8.3']
+                php: ['8.1', '8.2', '8.3', '8.4']
 
         steps:
             -   name: Checkout