feat: article on comment directives

## PR Checklist - [x] Addresses an existing open issue: fixes #142 - [x] That issue was marked as [accepting prs](https://github.com/LearningTypeScript/site/issues?q=is%3Aopen+is%3Aissue+label%3A%22accepting+prs%22) - [x] Steps in [CONTRIBUTING.md](https://github.com/LearningTypeScript/site/blob/main/.github/CONTRIBUTING.md) were taken ## Overview <!-- Description of what is changed and how the code change does that. -->