Move config from setup.cfg to pyproject.toml

(And to .flake8 because Flake8 won't support pyproject.toml)

Author: hugovk

Diff for: setup.cfg renamed to .flake8

@@ -1,6 +1,3 @@
 [flake8]
 max-line-length = 88
 extend-ignore = E203
-
-[isort]
-profile = black

Diff for: pyproject.toml

@@ -47,5 +47,8 @@ version-strings = ["pytest_sugar.py"]
 tag-prefix = "v"
 build-system = "setuptools"
 
+[tool.isort]
+profile = "black"
+
 [build-system]
 requires = ["setuptools >= 40.6.0", "wheel"]