📝 Documentation: GitHub Icon on Homepage

### Bug Report Checklist - [X] I have pulled the latest `main` branch of the repository. - [X] I have [searched for related issues](https://github.com/JoshuaKGoldberg/boston-ts-website/issues?q=is%3Aissue) and found none that matched my issue. ### Overview GitHub icon would be awesome linking to this repo on the website. ### Additional Info _No response_