Add danger check for duplicate yarn dependencies

Closes #51226

See merge request gitlab-org/gitlab-ce!21591

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.

Update eslint dependencies

See merge request gitlab-org/gitlab-ce!23610