Restructure repo and add workflow for reproducing results

[finsberg]

• Add jupyter-book config to the root folder
• Switch to use pyproject.toml together with pip-compile to generate dependencies (see https://hynek.me/til/pip-tools-and-pyproject-toml/)
• Use ruff rather than flake8 + reorder-python-imports + pyupgrade
• Update all github actions workflows
• Add caching to workflows
• Change demo from notebook to python file and use jupytext to convert it during building of the book
• Make all script have a command line interface
• Add new workflow for reproducing results