Add PHP 8.3 to test suite

Author: curry684

.github/workflows/tests.yml

@@ -12,7 +12,7 @@ jobs:
     runs-on: ubuntu-latest
     strategy:
       matrix:
-        php: ['8.1', '8.2']
+        php: ['8.1', '8.2', '8.3']
 
     name: "Tests"