Description of the problem, including code/CLI snippet

I would like to be able to call the /projects/:id/merge_requests/:iid/approval_rules endpoint as well as associated gets and updates.

https://docs.gitlab.com/ee/api/merge_request_approvals.html#get-merge-request-level-rules
https://docs.gitlab.com/ee/api/merge_request_approvals.html#create-merge-request-level-rule
https://docs.gitlab.com/ee/api/merge_request_approvals.html#update-merge-request-level-rule

Expected Behavior

Being able to call the endpoint, being able to get a list of approval_rules, create new rules, and update them.

Actual Behavior

Endpoint not exposed in python-gitlab API

Specifications

• python-gitlab version: latest
• API version you are using (v3/v4): v4
• Gitlab server version (or gitlab.com): latest

FYI

I actually have a branch where I've implemented this. PR should be up soon