Ability to add reviewers on commit page (BB-7545)

Would be awesome if I could add participants that I'd like to review a particular commit (for example https://bitbucket.org/atlassian/notifications-plugin/commits/3bcd2197f941/) on the commit page. BB should then notify these people to take a look at the commit.

At the moment I have to notify people manually to take a look at a commit. (I'm doing super lightweight code reviews. Don't want to do the full branching/pull request for this project).