Require slevomat/coding-standard

Author: mmoll

composer.json

@@ -25,7 +25,8 @@
         "issues": "https://github.com/djoos/Symfony-coding-standard/issues"
     },
     "require": {
-        "squizlabs/php_codesniffer": "^3.3.1"
+        "squizlabs/php_codesniffer": "^3.3.1",
+        "slevomat/coding-standard": "^7.0"
     },
     "require-dev": {
         "phpunit/phpunit": "^5.0 || ^6.0 || ^7.0"