Add pre-commit hook config to run flake8 and black on commit (#864)

Notes added to README on how to install and set up

.pre-commit-config.yaml

@@ -0,0 +1,15 @@
+repos:
+  - repo: https://github.com/pycqa/flake8
+    rev: 6.1.0
+    hooks:
+      - id: flake8
+        language_version: python3
+        args: [
+          '--extend-ignore=E203,W503',
+          '--max-line-length=100'
+        ]
+  - repo: https://github.com/psf/black
+    rev: 22.3.0
+    hooks:
+      - id: black
+        language_version: python3

CONTRIBUTING.md

@@ -95,6 +95,13 @@ Run the following commands from the root of the Parsons repository to lint your
 > black parsons
 ```
 
+Pre-commit hooks are available to enforce black and isort formatting on
+commit. You can also set up your IDE to reformat using black and/or isort on
+save.
+
+To set up the pre-commit hooks, install pre-commit with `pip install
+pre-commit`, and then run `pre-commit install`.
+
 #### Coding Conventions
 
 The following is a list of best practices to consider when writing code for the Parsons project: