Label bot PRs skip-changelog (#487)

Author: akihironitta

.github/workflows/dependabot-auto-merge.yml

@@ -14,11 +14,15 @@ jobs:
     runs-on: ubuntu-latest
     if: ${{ github.event.pull_request.user.login == 'dependabot[bot]' || github.event.pull_request.user.login == 'pre-commit-ci[bot]' }}
     steps:
+      - name: Label bot PRs
+        run: gh pr edit --add-label "ci,skip-changelog" ${{ github.event.pull_request.html_url }}
+        env:
+          GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
+
       - name: Auto-approve
         uses: hmarr/auto-approve-action@v4
 
       - name: Enable auto-merge
-        run: gh pr merge --auto --squash "$PR_URL"
+        run: gh pr merge --auto --squash ${{ github.event.pull_request.html_url }}
         env:
-          PR_URL: ${{github.event.pull_request.html_url}}
-          GITHUB_TOKEN: ${{secrets.GITHUB_TOKEN}}
+          GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}