placement of slides

.github/workflows/ci.yml

@@ -43,7 +43,7 @@ jobs:
       - name: Deploy to gh-pages branch
         run: |
           mkdir -p .
-          mv talk/slides.html index.html
+          cp talk/slides.html index.html
           cp -r talk/figures figures
           git add index.html
           git add -f talk/figures