Add pre-commit hooks for ruff

[claydugo]

I did this with their recommended setup where you specify a revision.

You can alternatively set it up to use the users ruff binary with something like:

repos:
  - repo: local
    hooks:
      - id: ruff
        name: ruff
        entry: ruff check .
        language: system

This is opt-in and requires running pre-commit install. Otherwise the current manual workflow still applies.

[fyellin]

It's probably too late. But I just saw the README.md, and I have absolutely no idea what it means.

Optionally, if you install pre-commit hooks with pre-commit install, lint fixes and formatting will be automatically applied on git commit.

Is pre-commit install a command I'm supposed to type at the shell? (It doesn't work). Is it a git command? (There is no such git command). From searching the web, it appears that this is a Python package that I'm supposed to install. We shouldn't make readers of READER.md have to search the web. Maybe pre-commit should be part of the pip -e .[dev]. ?