ci: update CD workflow and dependencies

- Rename workflow name from 'deploy' to 'cd'
- Upgrade actions/checkout from v3 to v4
- Upgrade peaceiris/actions-gh-pages from v3 to v4

Author: fulleni

.github/workflows/deploy.yml

@@ -1,4 +1,4 @@
-name: deploy
+name: cd
 
 # Run this workflow when a new release is published
 on:
@@ -11,7 +11,7 @@ jobs:
     steps:
       # 1. Checkout the repository code
       - name: Checkout
-        uses: actions/checkout@v3
+        uses: actions/checkout@v4
 
       # 2. Setup Flutter SDK
       - name: Setup Flutter
@@ -29,7 +29,7 @@ jobs:
 
       # 5. Deploy the built app to GitHub Pages
       - name: Deploy
-        uses: peaceiris/actions-gh-pages@v3
+        uses: peaceiris/actions-gh-pages@v4
         with:
           github_token: ${{ secrets.GITHUB_TOKEN }}
           publish_dir: ./build/web