chore: run tests on PHP 8.3

Author: bepsvpt

.github/workflows/testing.yml

@@ -61,7 +61,7 @@ jobs:
       fail-fast: false
 
       matrix:
-        php: [ '8.2', '8.1' ]
+        php: [ '8.3', '8.2', '8.1' ]
 
     steps:
       - uses: actions/checkout@v4