Add danger_local Rake task

What does this MR do and why?

Allow contributors to the project to pick up Danger warnings and errors locally.

How to set up and validate locally

1. Configure a local GitLab Docs environment: https://gitlab.com/gitlab-org/gitlab-docs/-/blob/main/doc/setup.md.
2. Check out this branch.
3. Make a change and add a new commit with a commit subject that violates commit message guidelines: https://docs.gitlab.com/ee/development/contributing/merge_request_workflow.html#commit-messages-guidelines. For example, the commit subject test..
4. Run make check-danger.
5. Run yarn run lefthook run pre-push.

Merge request acceptance checklist

This checklist encourages us to confirm any changes have been analyzed to reduce risks in quality, performance, reliability, security, and maintainability.

• I have evaluated the MR acceptance checklist for this merge request.