feat: article 'Why TypeScript Doesn't Include a `throws` Keyword'

## PR Checklist - [x] Addresses an existing open issue: fixes #138 - [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 Adds the article covering why the throw types seem nice, all the blockers to having them in JS/TS, and some preferred alternatives.