Test PHP8.1 (#544)

* Test PHP8.1

* Test php8.1 on L8

Author: barryvdh

.github/workflows/run-tests.yml

@@ -32,7 +32,10 @@ jobs:
           - laravel: ^8
             php: 7.3
             dependency-version: prefer-lowest
-
+          - laravel: ^8
+            php: 8.1
+            dependency-version: prefer-stable
+            
     name: P${{ matrix.php }} - L${{ matrix.laravel }} - ${{ matrix.dependency-version }}
 
     steps: