CI: fix permissions to deploy GitHub Pages

Also upgrade to actions-gh-pages@4.

Signed-off-by: Daniel Maslowski <[email protected]>

Author: orangecms

.github/workflows/gh-pages.yml

@@ -11,6 +11,8 @@ jobs:
     runs-on: ubuntu-24.04
     concurrency:
       group: ${{ github.workflow }}-${{ github.ref }}
+    permissions:
+      contents: write
     steps:
       - name: Checkout
         uses: actions/checkout@v4
@@ -30,7 +32,7 @@ jobs:
           mv book pages/
 
       - name: Deploy
-        uses: peaceiris/actions-gh-pages@v3
+        uses: peaceiris/actions-gh-pages@v4
         if: ${{ github.ref == 'refs/heads/main' }}
         with:
           github_token: ${{ secrets.GITHUB_TOKEN }}