Add .gitlab-ci.yml file

Problem/Motivation

The project is currently missing a .gitlab-ci.yml file. Adding the file will allow maintainers and contributing developers to run the Drupal CI/CD pipeline to ensure compliance with Drupal coding standards and allows to run test when added.

Steps to reproduce

• The .gitlab-ci.yml file is missing from the code repository.

Proposed resolution

• Add and configure the .gitlab-ci-.yml file

Remaining tasks

• See above

User interface changes

• None

API changes

• None

Data model changes

• None