Test against PHP 8.1

Author: aarondfrancis

.github/workflows/tests.yml

@@ -15,7 +15,7 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        php: [ 7.3, 7.4, 8.0 ]
+        php: [ 7.3, 7.4, 8.0, 8.1 ]
         laravel: [ 7.*, 8.*, 9.* ]
         dependency-version: [ prefer-lowest, prefer-stable ]
         include: