To add a new repository to the solutions list add a new entry like this for GitHub-hosted repos (sorted alphabetically, please 🙏):
- [username/repository](https://github.com/username/repository) 
or like this for non-GH repos:
- [username/repository](https://somewhere-else.com/username/repository)
Repositories not hosted on GitHub are fine, but they won't have a "last commit" badge.