Add example Drone config

Ref #13

.drone.yml

@@ -0,0 +1,32 @@
+---
+kind: pipeline
+name: deploy to docker container
+steps:
+  - name: docker cp deploy
+    image: 3wordchant/docker-cp-deploy:latest
+    settings:
+      host: <HOSTNAME>
+      service: <APP NAME>_php
+      chdir: src
+      exec: "composer install"
+      source: "composer.json composer.lock"
+      dest: /app/
+      deploy_key:
+        from_secret: <SSH KEY DRONE SECRET NAME>
+  - name: notify on failure
+    image: plugins/slack
+    settings:
+      username: comradebritney
+      channel: internal.builds
+      template: "{{repo.owner}}/{{repo.name}} build failed: {{build.link}}. Last commit by @{{build.author}}"
+      webhook:
+        from_secret: rc_builds_url
+    depends_on:
+      - docker cp deploy
+    when:
+      status:
+        - failure
+
+trigger:
+  branch:
+    - main