Add yarn script commands for Drupal coding standard and Drupal Practice for Varbase Carousels

Problem/Motivation

Saving time on checking standards and practice before committing any code.

#3112172: Drupal 9 compatibility for [Varbase Carousels] with Drupal coding standard and practice

---

Drupal coding standard and Drupal Practice check should pass

PHPCS, PHPCBF for both --standard=Drupal and --standard=DrupalPractice

Check Varbase Carousels Drupal coding standard

phpcbf --standard=Drupal --extensions=php,module,inc,install,test,theme,scss,css,info,txt,md,yml /var/www/html/products/varbase_carousels/ 

phpcs --standard=Drupal --extensions=php,module,inc,install,test,theme,scss,css,info,txt,md,yml /var/www/html/products/varbase_carousels/ 

Check Varbase Carousels Drupal Practice

phpcbf --standard=DrupalPractice --extensions=php,module,inc,install,test,theme,scss,css,info,txt,md,yml /var/www/html/products/varbase_carousels/ 

phpcs --standard=DrupalPractice --extensions=php,module,inc,install,test,theme,scss,css,info,txt,md,yml /var/www/html/products/varbase_carousels/

Proposed resolution

yarn phpcs
yarn phpcbf

as

  "scripts": {
    "phpcs": "phpcs --standard=./.phpcs.xml .",
    "phpcbf": "phpcbf --standard=./.phpcs.xml ."
  },