Rich Text Editor should respect the `r` shortcut

Summary

The Rich Text Editor doesn't respect the r shortcut at all.

Steps to reproduce

1. Go to any issue, MR or Epic.
2. Enable Rich Text Editor.
3. Enable shortcuts.
4. Click the reply to comment button on any comment.
5. Highlight some text in the comment.
6. Press r.
7. Notice nothing happens.

Example Project

Any MR, Issue, Epic.

What is the current bug behavior?

Nothing happens

What is the expected correct behavior?

Selected text is copied into the editor as a blockquote

Relevant logs and/or screenshots

Output of checks

Results of GitLab environment info

Expand for output related to GitLab environment info

(For installations with omnibus-gitlab package run and paste the output of: \`sudo gitlab-rake gitlab:env:info\`) (For installations from source run and paste the output of: \`sudo -u git -H bundle exec rake gitlab:env:info RAILS_ENV=production\`)

Results of GitLab application Check

Expand for output related to the GitLab application check

(For installations with omnibus-gitlab package run and paste the output of: `sudo gitlab-rake gitlab:check SANITIZE=true`)

(For installations from source run and paste the output of: `sudo -u git -H bundle exec rake gitlab:check RAILS_ENV=production SANITIZE=true`)

(we will only investigate if the tests are passing)

Possible fixes