Add drone with codestyle check

.drone.yml

@@ -0,0 +1,18 @@
+kind: pipeline
+name: default
+
+clone:
+  depth: 42
+
+steps:
+  - name: composer
+    image: joomlaprojects/docker-tools:develop
+    commands:
+      - composer validate --no-check-all --strict
+      - composer install --no-progress --no-suggest
+  - name: phpcs
+    image: joomlaprojects/docker-images:php7.2
+    commands:
+      - echo $(date)
+      - ./vendor/bin/phpcs --report=full --encoding=utf-8 --extensions=php -p --standard=./vendor/joomla/coding-standards/Joomla ./src
+      - echo $(date)

composer.json

@@ -0,0 +1,20 @@
+{
+    "name"       : "joomla-extensions/testing-sample-data",
+    "description": "Joomla Testing sample data plugin.",
+    "license"    : "GPL-2.0-or-later",
+    "config": {
+        "platform": {
+            "php": "7.2.23"
+        }
+    },
+    "require"    : {
+        "php": ">=7.2.0"
+    },
+    "require-dev": {
+        "joomla/cms-coding-standards": "~2.0.0-alpha2@dev",
+        "joomla/coding-standards": "~3.0@dev",
+        "friendsofphp/php-cs-fixer": "~2.12",
+        "squizlabs/php_codesniffer": "~3.0",
+        "dealerdirect/phpcodesniffer-composer-installer": "^0.5.0"
+    }
+}