Fixes GitHub action for docs deployment (#1239)

# Description

The docs were not deployed properly.

## Type of change

- Bug fix (non-breaking change which fixes an issue)

## Checklist

- [x] I have run the [`pre-commit` checks](https://pre-commit.com/) with
`./isaaclab.sh --format`
- [ ] I have made corresponding changes to the documentation
- [x] My changes generate no new warnings
- [ ] I have added tests that prove my fix is effective or that my
feature works
- [ ] I have updated the changelog and the corresponding version in the
extension's `config/extension.toml` file
- [x] I have added my name to the `CONTRIBUTORS.md` or my name already
exists there

.github/workflows/docs.yaml

@@ -25,6 +25,12 @@ jobs:
         working-directory: ./docs
         run: make html
 
+      - name: Upload docs artifact
+        uses: actions/upload-artifact@v4
+        with:
+          name: docs-html
+          path: ./docs/_build/html
+
   check-secrets:
     name: Check secrets
     runs-on: ubuntu-latest
@@ -45,6 +51,12 @@ jobs:
     if: needs.check-secrets.outputs.trigger-deploy == 'true'
 
     steps:
+      - name: Download docs artifact
+        uses: actions/download-artifact@v4
+        with:
+          name: docs-html
+          path: ./docs/_build/html
+
       - name: Deploy to gh-pages
         uses: peaceiris/actions-gh-pages@v3
         with: