Add isort configuration and pre-commit

.isort.cfg

+[settings]
+profile = black
+default_section = THIRDPARTY
+known_first_party = django
+

.pre-commit-config.yaml

+repos:
+  - repo: https://github.com/psf/black
+    rev: 22.1.0
+    hooks:
+    - id: black
+      language_version: python3.9
+  - repo: https://github.com/PyCQA/isort
+    rev: 5.9.3
+    hooks:
+      - id: isort
+  - repo: https://github.com/PyCQA/flake8
+    rev: 4.0.1
+    hooks:
+      - id: flake8