Pin isort hook to 5.6.4 (rapidsai#73)

Pins the `isort` pre-commit hook to 5.6.4 to correspond with the version bump in gpuCI (see rapidsai/integration#286). Also moves the pre-commit configuration to the root directory so it can be detected when running `pre-commit`.

Authors:
  - Charles Blackmon-Luca (https://github.com/charlesbluca)

Approvers:
  - https://github.com/jakirkham

URL: rapidsai#73

.pre-commit-config.yaml

@@ -0,0 +1,23 @@
+# To install the git pre-commit hook run:
+#   pre-commit install
+# To update the pre-commit hooks run:
+#   pre-commit install-hooks
+exclude: '^(\.tox|ci/templates|\.bumpversion\.cfg)(/|$)'
+repos:
+  - repo: https://github.com/pre-commit/pre-commit-hooks
+    rev: master
+    hooks:
+      - id: trailing-whitespace
+      - id: end-of-file-fixer
+      - id: debug-statements
+  - repo: https://github.com/pycqa/isort
+    rev: 5.6.4
+    hooks:
+      - id: isort
+        files: ^python/cucim/src/.*
+        args: ["--settings-path=python/cucim/setup.cfg"]
+  - repo: https://gitlab.com/pycqa/flake8
+    rev: master
+    hooks:
+      - id: flake8
+        files: ^python/cucim/.*