Add GitHub Codespaces support for easier testing

[mor10]

#21 adds full support for GitHub Codespaces through the addition of a devcontainer.json file.

This addition provides a one-click process for users to spin up the project and use the Realtime Console in their browser without needing to download the repo, configure Node.js, or run any processes locally.

Simply put, it just works.

These changes are nondestructive and agnostic. No project files have been changed and the Console still runs the same on any local or other system.