Allow Pull Request reviewers to 'like' lines of code on the overview tab

Can we have the ability to create positive feedback on the lines of code in the form of 'likes'.

This is a bit immature, but for me, reviewing a PR is finding the faults of the author of the pull request. It would be great if as a reviewer I can send positive feedback to the author, this can happen when I learned something new/think something is cool from the code or when a commit about your comment is pushed and I want to let the author know this is what I suggested.

I realize this is super trivial, so disregard this if you want haha