Only deploy pages on push and not pull request (#47)

Author: awvwgk

.github/workflows/gh-pages.yaml

@@ -42,7 +42,8 @@ jobs:
         make html
 
     - name: Deploy to GitHub Pages
+      if: github.event_name == 'push' && github.repository == 'microsoft/mattersim' && ( startsWith( github.ref, 'refs/tags/' ) || github.ref == 'refs/heads/main' )
       uses: peaceiris/actions-gh-pages@v3
       with:
         github_token: ${{ secrets.GITHUB_TOKEN }}
-        publish_dir: ./docs/_build/html
+        publish_dir: ./docs/_build/html