Visual Studio Code is one of the most popular IDEs these days. Contributing to it would probably be cool, but also extremely difficult. Given that is a mature product with millions of users, most likely the easy issues have all been addressed.

If you visit the web site the only indication as to how to contribute to it I found was a small GitHub logo at the bottom that leads to the GitHub repository of VS Code

As of this writing on 2023.06.18, it had more than 110,000 commits by 1,855 contributors. It also has 5K open issues and 405 open pull-requests. It is based on Electron and it is written in TypeScript.

In the README file in GitHub repository you can find a description on areas where one can contribute.