publish only if tag pushed

Author: boyan01

.github/workflows/publish.yml

@@ -59,4 +59,5 @@ jobs:
       # Publishing...
       - name: Publish to pub.dev
         run: flutter pub publish -f
+        if: startsWith(github.ref, 'refs/tags/')
         working-directory: 'packages/${{ steps.parse.outputs.result }}'