I (the creator of TimeSync) really appreciate you wanting to help out with the project and make it even better.
The project is in its early stages, and the project is not officiailly at a stage where it's accepting open-source contributions. Before I open the gates, I want to make sure that the three baseline packages (vanilla, React, Solid.js) are all working decently well and aren't likely to cause breaking API changes between each other.
However, if you find the project is interesting enough that you want to get involved early, I'm happy to collaborate. Right now, the best way to get started would probably be to open an issue or make a PR from a fork.