add Docker and Drone boilerplate

.drone.yml

@@ -0,0 +1,45 @@
+---
+kind: pipeline
+type: docker
+name: default
+
+steps:
+  - name: install
+    image: composer
+    volumes:
+      - name: composer-cache
+        path: /tmp/cache
+    environment:
+      COMPOSER_CACHE_DIR: /tmp/cache
+    commands:
+      - composer install --no-progress --no-interaction --no-dev --optimize-autoloader
+
+  - name: unit tests
+    image: php:7.4
+    commands:
+      - vendor/bin/phpunit -c phpunit.xml
+
+  - name: build image
+    image: docker
+    volumes:
+      - name: dockersock
+        path: /var/run/docker.sock
+    commands:
+      - docker build -t notecat:latest .
+
+  - name: deploy on testing
+    image: docker/compose
+    volumes:
+      - name: dockersock
+        path: /var/run/docker.sock
+    commands:
+      - docker-compose -f docker/docker-compose.testing.yml up --build --detach
+
+volumes:
+  - name: composer-cache
+    host:
+      path: /tmp/drone/composer-cache
+
+  - name: dockersock
+    host:
+      path: /var/run/docker.sock