pyproject.toml: Add tool.ruff.lint.extend-ignore

[cclauss]

% echo '\n[tool.ruff]\nlint.extend-ignore=["E4","E7","F40","F523","F601","F811","F841"]' >> pyproject.toml
% uvx pyproject-fmt pyproject.toml
% uvx validate-pyproject pyproject.toml

Valid file: pyproject.toml

% uvx ruff check

All checks passed!

As discussed at:

• GitHub Actions: Lint Python code with ruff mavlink/mavlink#2303

As tested at:

• DRAFT: Test ruff's monorepo processing mavlink/mavlink#2307

[amilcarlucas]

Thanks, merged