Add pr-comment.yaml action to default branch

.github/workflows/pr-comment.yaml

@@ -0,0 +1,25 @@
+name: Add PR comment
+
+on:
+  workflow_run:
+    workflows: ["Generate PDFs"]
+    types:
+      - completed
+
+jobs:
+  comment:
+    runs-on: ubuntu-latest
+    if: ${{ github.event.workflow_run.conclusion == 'success' }}
+    env:
+      GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
+      run_id: ${{ github.event.workflow_run.id }}
+    steps:
+      - name: Download artifacts
+        run: |
+          gh run download -n pdf $run_id
+          cat environ.txt >> $GITHUB_ENV
+
+      - name: Add PR comment
+        run: |
+          env
+          gh pr comment --body "Hello, this is dog." $pr_number