Add Slack Notifications (#78)

.github/workflows/build-on-push.yml

@@ -1,5 +1,13 @@
 name: Build
-on: [push]
+on:
+  push:
+    branches:
+      - '*'
+  pull_request:
+    branches:
+      - master
+  schedule:
+    - cron: "0 22 * * 1"
 jobs:
   build-referee:
     runs-on: ubuntu-latest
@@ -8,4 +16,14 @@ jobs:
       - uses: actions/setup-node@v1
       - run: sudo apt-get -qq update
       - run: sudo apt-get install -y oathtool
-      - run: yarn prepare-artifacts
+      - run: yarn prepare-artifacts
+      - name: Slack Notification on Master
+        if: ${{ failure() && github.ref == 'refs/heads/master'}}
+        uses: rtCamp/[email protected]
+        env:
+          SLACK_WEBHOOK: ${{ secrets.SLACK_WEBHOOK }}
+          SLACK_CHANNEL: referee-alerts
+          SLACK_MESSAGE: 'Cerberus main build has failed :build-failed:'
+          SLACK_ICON: https://github.githubassets.com/images/modules/logos_page/GitHub-Mark.png
+          SLACK_TITLE: Referee Build Failure Notification
+          SLACK_USERNAME: GitHub Actions