minor #422 Run tests on PHP 8.1 (derrabus)

This PR was merged into the 3.x-dev branch.

Discussion
----------

Run tests on PHP 8.1

Commits
-------

1c263a5 Run tests on PHP 8.1

Author: derrabus

.github/workflows/ci.yaml

@@ -11,7 +11,7 @@ jobs:
         strategy:
             fail-fast: false
             matrix:
-                php: [ '7.2', '7.3', '7.4', '8.0' ]
+                php: [ '7.2', '7.3', '7.4', '8.0', '8.1' ]
                 monolog: [ '1.*', '2.*' ]
                 include:
                     -   php: '7.1'