Add ci alerts (G-Research#1367)

* Add nudge workflow
---------

Co-authored-by: Jonathan Giannuzzi <jgiannuzzi@users.noreply.github.com>

.github/workflows/nudge.yml

@@ -0,0 +1,17 @@
+name: Nudge
+
+on:
+  workflow_run:
+    workflows: ["CI", "Create release", "Release", "Build and Deploy website to Pages"]
+    types: [completed]
+    branches: [main]
+
+jobs:
+  nudge:
+    runs-on: ubuntu-latest
+    environment: nudge
+    steps:
+      - name: Send message
+        uses: pavlovic-ivan/octo-nudge@main
+        with:
+          webhooks: ${{ secrets.WEBHOOKS }}