Provide an ability to create anchored link to an issue related issues & merge requests

Problem to solve

Currently there is no way to send a link with MRs related to specific issue OR issues related to specific issue and it would be very convenient in communication.

Intended users

Further details

Proposal

  • Add anchors #related-issues and #related-merge-requests to appropriate HTML blocks so a user can send a link to an issue explicitly focusing corresponding page blocks.
  • This would also require to introduce similar UI on hover as we have for h1\2\3\x tags in issue description, so the user can copy link with proper anchor.

See screenshot: Screenshot_2020-02-26_17.24.58

/cc @donaldcook