Support local development environment variables

[Robbe-Superlinear]

It’s recommended to use a .env file to securely manage sensitive configuration information, such as API keys, database credentials, and other environment-specific variables.

To ensure these configurations are used during development we should consider adding env_file to the devcontainer’s docker-compose configuration, pointing it towards the .env file.

As a result, the .env file should be added to the .gitignore file to prevent accidental inclusion in version control.