deploy gh pages only on master
deploy gh pages only on master

attempt to fix the action "Publish generated content to GitHub Pages" in PRs

````
2s
Run peaceiris/actions-gh-pages@v3
[INFO] Usage https://github.com/peaceiris/actions-gh-pages#readme
Dump inputs
Setup auth token
Prepare publishing assets
Setup Git config
Create a commit
Push the commit or tag
  /usr/bin/git push origin gh-pages
  remote: Permission to PyAr/PyZombis.git denied to github-actions[bot].
  fatal: unable to access 'https://github.com/PyAr/PyZombis.git/': The requested URL returned error: 403
  Error: Action failed with "The process '/usr/bin/git' failed with exit code 128"
````
PyAr/PyZombis,PyAr/PyZombis,PyAr/PyZombis