Merge pull request #83 from simPod/8.1

Test on PHP 8.1

Author: rtheunissen

.github/workflows/ci.yaml

@@ -21,6 +21,7 @@ jobs:
           - "7.3"
           - "7.4"
           - "8.0"
+          - "8.1"
         dependencies:
           - "highest"