Update '.drone.yml'

.drone.yml

@@ -8,3 +8,13 @@ steps:
   commands:
   - apt-get update && apt-get install --no-install-recommends -y docker-compose
   - docker-compose config --services
+
+- name: slack
+  image: plugins/slack
+  settings:
+    webhook:
+      from_secret: slack_webhook
+    channel: alerts-ci
+    icon_url: https://cloudcdn.tormakristof.eu/static/drone.svg
+  when:
+    status: [ failure ]