Test on PHP 8.1 (#34)

Author: simPod

.github/workflows/ci.yaml

@@ -70,7 +70,7 @@ jobs:
         runs-on: ubuntu-20.04
         strategy:
             matrix:
-                php-version: [8.0]
+                php-version: [8.0, 8.1]
                 dependencies: ["", --prefer-lowest]
 
         steps: