Bump CI, test with PHP 8.4

Author: derrabus

.github/workflows/tests.yml

@@ -25,10 +25,11 @@ jobs:
                     - '8.1'
                     - '8.2'
                     - '8.3'
+                    - '8.4'
 
         steps:
             -   name: Checkout
-                uses: actions/checkout@v3
+                uses: actions/checkout@v4
 
             -   name: Setup PHP
                 uses: shivammathur/setup-php@v2