Add VS Code devcontainer config

[bcdickinson]

Description

Adds a simple VS Code devcontainer setup for this project based on the existing docker-compose setup.

Closes #173

Checklist

• My code follows the style guidelines of this project
• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• My changes generate no new warnings
• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes
• I have added an appropriate CHANGELOG entry

[thibaudcolas]

@bcdickinson gave this a quick look, all seems fine to me. I’ll try running this locally once it’s merged 😬 .