pre-commit: add isort hook and apply (#354)

pyproject.toml

@@ -100,6 +100,15 @@ help = "Run tests with multiple pythons"
 cmd = "black . --check --diff"
 help = "Check if code style is correct"
 
+[tool.isort]
+py_version = 37
+profile = "black"
+force_single_line = false
+combine_as_imports = true
+lines_after_imports = 2
+include_trailing_comma = true
+force_grid_wrap = 2
+src_paths = ["src", "tests"]
 
 [tool.black]
 target-version = ['py36']