Great that you want to contribute to the EthereumJS ecosystem. EthereumJS is managed by the Ethereum Foundation and largely driven by the wider community. Everyone is welcome to join the effort and help to improve on the libraries (see our Code of Conduct 🌷).
We have written up some Contribution Guidelines to help you getting started.
These include information on how we work with Git and how our general workflow and technical setup looks like (stuff like language, tooling, code quality and style).
Happy Coding! 👾 😀 💻