Visual Studio Code Web Extension

GitHub recently integrated [Visual Studio Code in the browser](https://docs.github.com/en/codespaces/developing-in-codespaces/web-based-editor). When you press `.` while viewing a file on GitHub, it opens VSCode.

Users can install additional [web extensions](https://code.visualstudio.com/api/extension-guides/web-extensions), and it would be great to leverage the [recent language server / vscode](https://github.com/cucumber/common/pull/1689) code to build this extension.

This would give GitHub users a first-class editing experience on the web at GitHub.com.