Add danger check for duplicate yarn dependencies

What does this MR do?

This danger check utilises yarn-deduplicate in order to show duplicate dependencies in the yarn.lock dependency tree. Often when introducing new dependencies or updating existing ones, yarn does not seem to build the most optimal dependency tree.

In order to prevent those unnecessary dependency updates we are nudging developers and maintainers to resolve these issues in MRs. Automating this with danger especially helps, as yarn.lock files are not that easy to review.

Example output:

What are the relevant issue numbers?

• Closes #51226 (closed)
• Relates to: https://gitlab.com/gitlab-org/gitlab-ce/issues/51855

Does this MR meet the acceptance criteria?

• Changelog entry added, if necessary
• Documentation created/updated
• Tests added for this feature/bug
• Conforms to the code review guidelines
• Conforms to the merge request performance guidelines
• Conforms to the style guides
• Conforms to the database guides