Add a way to indicate that other users may complete checkboxes in my comments
Description
When reviewing an MR, it would be nice to be able to add checkboxes to my comment for things that need to be addressed. Currently, only owners, masters, and myself may check those boxes (due to edit perm restrictions).
Proposal
Something like adding <!-- gitlab_checkbox: @foo -->
to allow users to edit the comment (at least for checkboxes; probably not in the full editor). It'd also be nice to have shortcuts for things like the submitter.