0.7.0

• Drop support for Python 3.7 (end of life 2023-06-27), require Python 3.8.
• Add support for Python 3.12.
• Drop backwards compability with IPython.nbformat for IPython <4.
• Rename cell ids to be sequential by default. Disable by passing --keep-id (@JasonJooste, #184).
• Improve documentation for notebook and cell metadata stripping (#187).
• Switch from pytest-flake8 to pytest-ruff.
• Convert all text assets from rST to Markdown format.