Add pre-commit hook configuration

.pre-commit-config.yaml

@@ -0,0 +1,22 @@
+# Even these tools are configured in setup.cfg, it seems they don't take
+# configuration from there, and it's needed to pass the configuration as
+# arguments.
+repos:
+  # black order imports with several in a line if possible, while black put
+  # one by line.
+  - repo: https://github.com/pre-commit/mirrors-isort
+    rev: v4.3.21
+    hooks:
+      - id: isort
+  - repo: https://github.com/ambv/black
+    rev: 19.3b0
+    hooks:
+      - id: black
+        language_version: python3.7
+  - repo: https://github.com/pre-commit/pre-commit-hooks
+    rev: v2.3.0
+    hooks:
+      - id: flake8
+        additional_dependencies: [
+        'flake8-docstrings',
+        ]