Add initial devcontainer configuration for Rust environment

[luisgizirian]

Adds a .devcontainer folder with a single devcontainer.json file that allows you to develop in a rust-nightly ready container.

If using one of the supported editors (https://containers.dev/supporting) for your regular development and for any reason would prefer to run/test/compile in a container-based environment, this gets you a ready-to-go solution.

Issue #494