documentation #41: adding back publish on main only

.github/workflows/docs.yml

@@ -46,6 +46,7 @@ jobs:
 
   publish-docs:
     needs: build-docs
+    if: github.event_name == 'push' && github.ref == 'refs/heads/main'
     runs-on: ubuntu-22.04
     steps:
     - name: Download Documentation