documentation #41: upgrade CI

Author: FabienDanieau

.github/workflows/docs.yml

@@ -56,7 +56,7 @@ jobs:
         path: docs/
 
     - name: Deploy to GitHub Pages
-      uses: peaceiris/actions-gh-pages@v3
+      uses: peaceiris/actions-gh-pages@v4
       with:
         github_token: ${{ secrets.GITHUB_TOKEN }}
         publish_dir: ./docs