Add linter, checker configurations

.flake8

@@ -0,0 +1,11 @@
+[flake8]
+max-line-length = 119
+ignore = W503
+exclude =
+    .git,
+    __pycache__,
+    docs/source/conf.py,
+    old,
+    build,
+    dist,
+    migrations

.isort.cfg

@@ -0,0 +1,9 @@
+[settings]
+line_length = 60
+multi_line_output = 3
+use_parentheses = true
+include_trailing_comma = true
+quiet = true
+force_grid_wrap = 0
+known_django = django
+sections = FUTURE,STDLIB,DJANGO,THIRDPARTY,FIRSTPARTY,LOCALFOLDER

pyproject.toml

@@ -0,0 +1,17 @@
+[tool.black]
+line-length = 119
+py36 = true
+skip-string-normalization = true
+quiet = true
+exclude='''
+/(
+    \.git
+  | \.hg
+  | \.tox
+  | \.venv
+  | _build
+  | buck-out
+  | build
+  | dist
+)/
+'''