Show remaining approvals in merge requests
## Problem description
MRs in `gitlab-org/gitlab` often require many approvals. As a maintainer keeping track of this to know when a MR can be merged is difficult.
## Current behaviour
Our approval rules doesn't remedy this as it only needs 1 approval and the rest of the files are optional.
I've created MRs that require up to 8 approvals and in those cases I keep track of the approvals in a the MR description using checkboxes:

## Suggested solution
@terrichu suggested in a [comment](https://gitlab.com/gitlab-org/gitlab/-/merge_requests/86568#note_989502705) that we add this to dangerbot and I think that's a good idea. I'm not 100% sure how to do that for `gitlab-org/gitlab`, but I have some ideas:
1. Add checkboxes to the `Reviewer roulette` comment suggestions.
1. Add a dedicated comment that looks similar to the screenshot above.
1. Dynamically add a `Approvals` section to the bottom of the MR description based on labels / reviewer roulette.
issue