add flake8 and lint

#20

• add flake8 and lint

default virtualenv dir as .venv

#19

• change default virtualenv dir as .venv.

single-quote in pyproject.toml

#17

• single-quote in pyproject.toml

#18

• update license year to 2024.

with pyproject.toml

#16

• with pyproject.toml

README

#13

• update README.md and project/README.md

update test framework to pytest

#12

• update test framework to pytest