feat: add slack notifications on failed workflows

.github/workflows/release-plz.yaml

@@ -9,6 +9,9 @@ on:
       cargo_registry_token:
         description: 'Cargo registry token'
         required: true
+      slack_webhook:
+        description: 'Slack webhook for notifications'
+        required: true
     inputs:
       run_tests:
         type: boolean
@@ -60,6 +63,13 @@ jobs:
           GITHUB_TOKEN: ${{ secrets.gh_token }}
           CARGO_REGISTRY_TOKEN: ${{ secrets.cargo_registry_token }}
 
+      - name: Notify about failure
+        if: failure()
+        uses: matter-labs/format-release-please-for-slack-action@69e6fe9e4ec531b7b5fb0d826f73c190db83cf42 # v2.1.0
+        with:
+          release-please-output: '{ "body": "⚠️ Failed to publish the release" }'
+          slack-webhook-url: ${{ secrets.slack_webhook }}
+
   # Create a PR with the new versions and changelog, preparing the next release.
   release-plz-pr:
     name: Release-plz PR