Add .pre-commit-config.yaml

[grossir]

We need a pre-commit config that matches the PR checks:

eyecite/.github/workflows/lint.yml

Lines 50 to 63 in c89661f

	- name: Black Code Formatter
	uses: psf/black@stable
	- name: Run flake8
	uses: py-actions/flake8@v2
	- name: isort Import Sorter
	uses: isort/isort-action@v1
	- name: pylint Error Checker
	run: pylint --fail-under 9 -f colorized eyecite
	- name: mypy Static Type Checker
	run: mypy .

Courtlistener's config
https://github.com/freelawproject/courtlistener/blob/main/.pre-commit-config.yaml