Add PHP 8.4 to the workflow matrix (#112)

Since 8.0 is dead, what do you think of dropping it? PHP 8.5 will be out
in a few weeks, we could also add it to the matrix.

Author: mvdbos

.github/workflows/php.yml

@@ -14,7 +14,7 @@ jobs:
       fail-fast: false
       matrix:
         operating-system: [ ubuntu-latest ]
-        php-versions: [ '8.0', '8.1', '8.2', '8.3' ]
+        php-versions: [ '8.0', '8.1', '8.2', '8.3', '8.4' ]
 
     steps:
       - uses: actions/checkout@v5