Add Slack notifications

Author: xalopp

.github/workflows/ci.yml

@@ -101,3 +101,20 @@ jobs:
         with:
           verbose: true
 
+  slack-notify:
+    needs: [run-tests, style-checks]
+    if: always()
+    runs-on: ubuntu-latest
+    steps:
+      - uses: technote-space/workflow-conclusion-action@v2
+      - name: Post to a Slack channel
+        id: slack
+        uses: slackapi/slack-github-action@v1.17.0
+        with:
+          # Slack channel id, channel name, or user id to post message.
+          # See also: https://api.slack.com/methods/chat.postMessage#channels
+          channel-id: '#mo4'
+          # For posting a simple plain text message
+          slack-message: "GitHub build result: ${{ job.status }}\n${{ github.event.pull_request.html_url || github.event.head_commit.url }}"
+        env:
+          SLACK_BOT_TOKEN: ${{ secrets.SLACK_BOT_TOKEN }}