chore: report github actions failure on zulip (#4830)

only the master branch

.github/workflows/ci.yml

@@ -455,12 +455,24 @@ jobs:
     # mark as merely cancelled not failed if builds are cancelled
     if: ${{ !cancelled() }}
     steps:
+    - if: ${{ contains(needs.*.result, 'failure') && github.repository == 'leanprover/lean4' && github.ref_name == 'master' }}
+      uses: zulip/github-actions-zulip/send-message@v1
+      with:
+        api-key: ${{ secrets.ZULIP_BOT_KEY }}
+        email: "github-actions-bot@lean-fro.zulipchat.com"
+        organization-url: "https://lean-fro.zulipchat.com"
+        to: "infrastructure"
+        topic: "Github actions"
+        type: "stream"
+        content: |
+          A build of `${{ github.ref_name }}`, triggered by event `${{ github.event_name }}`, [failed](https://github.com/${{ github.repository }}/actions/runs/${{ github.run_id }}).
     - if: contains(needs.*.result, 'failure')
       uses: actions/github-script@v7
       with:
         script: |
             core.setFailed('Some jobs failed')
 
+
   # This job creates releases from tags
   # (whether they are "unofficial" releases for experiments, or official releases when the tag is "v" followed by a semver string.)
   # We do not attempt to automatically construct a changelog here: