Add PHP 8.3 to tests workflow

Author: wasinger

.github/workflows/tests.yml

@@ -15,7 +15,7 @@ jobs:
 
     strategy:
       matrix:
-        php: [8.0, 8.1, 8.2]
+        php: [8.0, 8.1, 8.2, 8.3]
         dependency-version: [prefer-lowest, prefer-stable]
 
     steps: