limits job to run only if PR workflow completed successfully

Author: gilzow

.github/workflows/comment-on-pr.yaml

@@ -12,6 +12,7 @@ on:
 jobs:
   comment:
     runs-on: ubuntu-latest
+    if: ${{ github.event.workflow_run.conclusion == 'success' }}
     steps:
       - uses: actions/checkout@v2