fix(ci): publish docs only for main branch

Author: machow

.github/workflows/ci.yml

@@ -85,6 +85,7 @@ jobs:
     name: "Publish Docs"
     runs-on: ubuntu-latest
     needs: ["build-docs", "tests", "test-rsconnect"]
+    if: github.ref == 'refs/heads/main'
     steps:
       - uses: actions/download-artifact@v3
         with: