TRACKING: Follow-up to black transition

[neiljp]

• Add black 'badge' to README
• Document basic expected style (isort + black?)
• Document auto-fixing code at base level & editor integration
• Pre-commit hook?
• Migrate to zulint (may require updates to earlier categories)
• Consider deprecation of flake8 settings, use of autopep8, use of autoflake; use of pyflakes?

[andersk]

• Consider applying Black to setup.py and tools/*, which were initially excluded (discussion).

[neiljp]

#1192 resolves second point.

[neiljp]

Marking flake8 settings and similar as completed, since we have migrated to ruff.