CI: run PHP 8.4 (#16)

Author: janedbal

.github/workflows/checks.yml

@@ -32,7 +32,7 @@ jobs:
         strategy:
             fail-fast: false
             matrix:
-                php-version: [ '8.1', '8.2', '8.3' ]
+                php-version: [ '8.1', '8.2', '8.3', '8.4' ]
                 doctrine-version: [ '^2.19', '^3.2' ]
                 dependency-version: [ prefer-lowest, prefer-stable ]
         steps: