Adding some code formatting and linters

[shivan-s]

Do you think it will be helpful to add code linters/formatters such as:

• flake8 - https://flake8.pycqa.org/en/latest/
• mypy (maybe not because this project isn't typed) - https://www.mypy-lang.org/
• black - https://black.readthedocs.io/en/stable/index.html

And a pre-commit (https://pre-commit.com/) to run the above with every commit.