Reproducible development environments with VSCode devcontainers

If devcontainer is set to "y" project uses the VSCode devcontainer specification to create a reproducible development environment. The devcontainer is defined in the .devcontainer directory and pre-installs all dependencies from poetry required to develop, test and build the project.

The devcontainer also installs the pre-commit hooks and configures the VSCode python extension to use the appropriate python interpretor and pytest paths.