ci: update Checkout GitHub Action to v4 (#17)

Author: LayZeeDK

.github/workflows/website.yml

@@ -17,7 +17,7 @@ jobs:
     runs-on: ubuntu-latest
 
     steps:
-      - uses: actions/checkout@v2
+      - uses: actions/checkout@v4
       - name: Use Node.js ${{ env.node-version }}
         uses: actions/setup-node@v4
         with: