Add PHP 8.1 to tests matrix

Author: ifox

.github/workflows/run-tests.yml

@@ -19,7 +19,7 @@ jobs:
 
     strategy:
       matrix:
-        php: [8.0, 7.4, 7.3, 7.2]
+        php: [8.1, 8.0, 7.4, 7.3, 7.2]
 
     name: P${{ matrix.php }}