Devcontainer

As a developer I want to easily get going with this project without having to worry about my version of node et al.

## Possible Solution

Use [devcontainers](https://containers.dev/). Ideally we should be able to use a pre-built container rather than making our own Dockerfile, which would slow down the setup process considerably.

## Acceptance Criteria
- There is a devcontainer definition in the repository
- It provides the tools needed to build and run the project in dev mode