Configure release-it for this project

We would benefit strongly from having release-it configured.

• Add a runner for this project (and gcp-deploy-boilerplate) which uses the shared code GCP infra (uis/devops/devhub/gitlab-runner-infrastructure!163).
• Add a GitLab token secret for this project (and gcp-deploy-boilerplate but not the uis/devops/group) in the GitLab project factory. Give the appropriate runner SAs access.
• Add commitlint CI configuration to this repo to ensure CHANGELOG generation works.
• Add release-it CI configuration to this repo, overriding the GITLAB_ACCESS_TOKEN_SECRET_ID variable appropriately.

There is some fiddling required since these projects live in the top-level group so we don't want to accidentally add config which is inherited by sub-groups. Of course we could move these projects but, at least for the webapp repo, there are a lot of .copier-answers.yml files which would need updating.