Move development repository to Gitlab

Problem/Motivation

At the moment, we create PRs on the CivicTheme development repository: https://github.com/civictheme/monorepo-drupal

When changes are accepted there we publish those changes to the https://git.drupalcode.org/project/civictheme/tree/1.x

This creates a dislocation between Drupal community and development work

This ticket to create discussion and begin moving to an improved contribution model.

Proposed resolution

1. Drupal theme commits are made via MR to the Gitlab infrastructure and invert the source of truth for the development process.

Remaining tasks

1. Create gitlab actions that publish back to the GitHub development repository (inverting the current flow)