Add comments and see related MRs on board issue detail sidebar

This issue is being tracked as part of https://gitlab.com/gitlab-org/gitlab-ee/issues/13319

Problem to solve

If you're at an issue board and click on an issue where the details of the issue open at the sidebar, you don't have the possibility to simply add a comment or see related MRs. You always have to click the issue to get into the detail view page, to see that and to create a comment.

Intended users

Developers, Reviewers

Further details

Improves simplicity and efficiency.

Proposal

It would be very nice if there is the possibility at the sidebar to add a comment and see related PRs.

What is the type of buyer?

Not sure, at least in starter I guess. Maybe free tier too.

Links / references