add some isort and flake8 config

Author: janosh

setup.cfg

@@ -0,0 +1,12 @@
+[flake8]
+max-line-length = 100
+exclude = .git
+# E731: do not assign a lambda expression, use a def
+# W503: line break before binary operator
+ignore = E731, W503
+
+# Make isort play nicely with black's import formatting.
+# https://github.com/microsoft/vscode-python/issues/5840
+[isort]
+multi_line_output = 3
+include_trailing_comma = True