Add PHP 8.5 to CI matrix (#22)

Author: ruudk

.github/workflows/ci.yaml

@@ -21,6 +21,7 @@ jobs:
                     - '8.2'
                     - '8.3'
                     - '8.4'
+                    - '8.5'
                 dependency-versions: [ lowest, highest ]
         steps:
             -   name: Checkout