Document review guidelines for Docs engineering

### Kanban process

Move issues through **Ready for development** → **In dev** → **In review** → **Closed**. In general, work is "done" when deployed and documentation is complete.

### Review and testing guidelines

All code changes should be reviewed by another engineer. These reviews should follow

general GitLab [code review best practices](https://docs.gitlab.com/development/code_review/#best-practices). For complex changes, or changes that could impact team workflows, consider tagging multiple reviewers.

Changes to the look and feel of the site, especially global changes that can impact usability, should also be UX reviewed by a Staff+ Technical Writer or manager.

New shortcodes or other writer-facing features should be tested by a Staff+ Technical Writer or manager, then documented in the [style guide](https://docs.gitlab.com/development/documentation/styleguide/).