Switch to shared CI configuration

.gitlab-ci.yml

-variables:
-  # Configure mysql service (https://hub.docker.com/_/mysql/)
-  MYSQL_DATABASE: wordpress_tests
-  MYSQL_ROOT_PASSWORD: mysql
-
-cache:
-  paths:
-    - $HOME/.composer
-    - /root/.composer
-
-before_script:
-  # Set up WordPress tests
-  - bash bin/install-wp-tests.sh $MYSQL_DATABASE root $MYSQL_ROOT_PASSWORD mysql latest true
-
-  # PHPUnit
-  - |
-    if [[ $(php -v) =~ "PHP 7." ]]; then
-      composer global require "phpunit/phpunit=6.1.*"
-    else
-      composer global require "phpunit/phpunit=4.8.*"
-    fi
-
-  # Install PHPCS and WPCS
-  - composer global require automattic/vipwpcs
-  - phpcs --config-set installed_paths $HOME/.composer/vendor/wp-coding-standards/wpcs,$HOME/.composer/vendor/automattic/vipwpcs
-
-PHPunit:PHP7.0:MySQL:
-  image: containers.ethitter.com:443/docker/images/php:7.0
-  services:
-    - mysql:5.6
-  script:
-    - phpcs -n
-    - phpunit
-
-PHPunit:PHP7.1:MySQL:
-  image: containers.ethitter.com:443/docker/images/php:7.1
-  services:
-    - mysql:5.6
-  script:
-    - phpcs -n
-    - phpunit
-
-PHPunit:PHP7.2:MySQL:
-  image: containers.ethitter.com:443/docker/images/php:7.2
-  services:
-    - mysql:5.6
-  script:
-    - phpcs -n
-    - phpunit
+include:
+  - remote: https://git.ethitter.com/gitlab/ci/wordpress/-/raw/main/plugins/default.yml