Extracted list of config filename so that it can be overriden

[wieczorek1990]

Please see related:
csachs/pyproject-flake8#14

[sadikkuzu]

Hi @wieczorek1990

I may miss something.
What is the difference between:

for candidate in ("setup.cfg", "tox.ini", ".flake8"):

and

CONFIG_FILENAMES = ("setup.cfg", "tox.ini", ".flake8")
for candidate in CONFIG_FILENAMES:

?

Thanks, have a nice day.

[wieczorek1990]

This way some other package can extend the list. No easy way to extend a tuple used in a function.
Same usage before version 5:
https://github.com/csachs/pyproject-flake8/blob/main/pflake8/__init__.py#L57

[asottile]

monkeypatching is not supported