Show Related Merge Requests in "Issues" List

Description

When I started looking for issues I could work on, I noticed that it gets quite annoying to open each issue and check whether there already is any merge request for the issue. This could also be benefitting for project maintainers in the same sense.

Proposal

Add a small icon to the "Issues" list that states how many Merge Requests are related to this issue:

tooltip:

Maybe the number of related merge requests could be removed from the list and only be visible in the tooltip, making it more minimal.

Links / references

I have already worked on this locally and will open a merge request.