Use uv

[nickmoreton]

This pull request introduces significant updates to the Wagtail WordPress Import package

• Transition to 'uv' for Python packaging etc.

Packaging and Build System Updates:

• Migrated the build system to use hatchling with configuration in pyproject.toml, replacing setup.py and setup.cfg.

Development Tooling Enhancements:

• Replaced black, flake8, and isort with ruff for linting and formatting.

Documentation Improvements:

• Updated docs/development.md guide detailing the development setup, tools, and processes for contributors.
• Enhanced the README.md with updated installation instructions, a new development setup section, and links to the development guide.
• Updated docs/tooling.md to reflect the new development tools and link to the development guide.

Configuration and Coverage Updates:

• Refactored .coveragerc to include additional directories in the omit list and updated coverage reporting settings.
• Added configuration for generating HTML and XML coverage reports.

Ticket URL:

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Testing

• CI passes
• If necessary, tests are added for new or fixed behaviour
• These changes do not reduce test coverage

Documentation.

• This PR adds or updates documentation
• Documentation changes are not necessary because: