build: skip dockerhub login if it's a PR (#373)

Author: enapupe

.github/workflows/nodejs.yml

@@ -82,6 +82,7 @@ jobs:
 
       - name: Login to DockerHub
         uses: docker/login-action@v2
+        if: github.event_name != 'pull_request'
         with:
           username: ${{ secrets.DOCKERHUB_USERNAME }}
           password: ${{ secrets.DOCKERHUB_TOKEN }}