Add PHP codesniffer to dev requirements

Author: jradcliff

google-analytics-data/composer.json

@@ -4,6 +4,7 @@
  },
  "require-dev": {
  "google/cloud-tools": "dev-main",
+ "squizlabs/php_codesniffer": "^3.5",
  "phpunit/phpunit": "^9.0"
  }
 }