test: add test for php 8.4

Author: Sysix

.github/workflows/tests.yml

@@ -14,7 +14,7 @@ jobs:
     strategy:
       fail-fast: true
       matrix:
-        php: [8.3, 8.2, 8.1]
+        php: [8.4, 8.3, 8.2, 8.1]
         dependency-version: [prefer-lowest, prefer-stable]
 
     name: PHP${{ matrix.php }} - ${{ matrix.dependency-version }}