Basic fmt command

[cnpryer]

huak fmt

Run huak fmt to format python code.

The first version of fmt would:

• Execute black using .venv-installed black.
• Use pep-adhering black configuration like --line-length 79.
• Execute isort using .venv-installed isort.
• Use black-compatible isort configuration like:

[tool.isort]
multi_line_output = 3
line_length = 79
include_trailing_comma = true

• Add --check flag.