Update PHP to 8.3

Author: donatj

.github/workflows/ci.yml

@@ -11,7 +11,7 @@ jobs:
     strategy:
       matrix:
         operating-system: [ ubuntu-latest ]
-        php-versions: [ '7.4', '8.0', '8.1', '8.2' ]
+        php-versions: [ '7.4', '8.0', '8.1', '8.2', '8.3' ]
 
     runs-on: ${{ matrix.operating-system }}