Add PHP 8.4 to test matrix (#22)

Author: OskarStark

.github/workflows/ci.yaml

@@ -45,6 +45,7 @@ jobs:
                     - '8.1'
                     - '8.2'
                     - '8.3'
+                    - '8.4'
                 dependencies:
                     - 'highest'
                     - 'lowest'