Add devcontainer.json

[jungaretti]

Adds a devcontainer.json file that lets you explore this repo seamlessly with GitHub Codespaces.

Create a new codespace for this branch to test it out: https://github.com/codespaces/new?ref=add-devcontainer&repo=580865109

Learn more about dev containers: https://docs.github.com/en/codespaces/setting-up-your-project-for-codespaces/introduction-to-dev-containers

Learn more about Codespaces: https://docs.github.com/en/codespaces/getting-started/quickstart