chore: update readme example to use checkout@v5 (#7)

Author: ppvg

README.md

@@ -21,7 +21,7 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - name: Checkout repository
-        uses: actions/checkout@v4
+        uses: actions/checkout@v5
 
       - name: Install dependencies
         uses: minvws/action-php-composer-install@v1