tests: add tests for PHP 8.4 (#568)

.github/workflows/continuous-integration.yml

@@ -79,6 +79,7 @@ jobs:
           - "8.1"
           - "8.2"
           - "8.3"
+          - "8.4"
         include:
           # Keep the locked version by default
           - dependency-versions: "locked"
@@ -156,6 +157,7 @@ jobs:
           - "8.1"
           - "8.2"
           - "8.3"
+          - "8.4"
         operating-system:
           - "ubuntu-latest"
           - "windows-latest"