Run checks for PHP 8.1

Author: Jakub-Fajkus

.github/workflows/php-package-ci.yml

@@ -9,7 +9,7 @@ jobs:
     runs-on: ubuntu-latest
     strategy:
       matrix:
-        php: [ 7.4, 8.0 ]
+        php: [ 7.4, 8.0, 8.1]
     steps:
       - uses: actions/checkout@v2
       - uses: shivammathur/setup-php@v2