- Use ruff and yapf for the targets py-check-syntax, py-format and
py-check-format.
- Add a pyproject.toml for those. It also includes configuration
for isort, albeit not being directly used in the linter targets.
- Make .gitignore igore that in newly created projects.
- Add ruff, yapf and isort to pkg.requires.release, anticipating
their use by CI.
Signed-off-by: Jan Lindemann <jan@janware.com>