Add links to code review technical guides

[OleksiyRudenko]

The following links might be a part of supplementary materials at code-review-guidelines.md

• https://lab.github.com/githubtraining/reviewing-pull-requests
• https://help.github.com/articles/about-pull-request-reviews/
• https://help.github.com/articles/reviewing-proposed-changes-in-a-pull-request/

[zonzujiro]

You can just create a PR instead.