Add a pre-commit hook definition

[bittner]

Adds a .pre-commit-hooks.yaml so the formatter can be used directly as a pre-commit hook:

- repo: https://github.com/nvuillam/markdown-table-formatter
  rev: v1.7.0
  hooks:
  - id: markdown-table-formatter

Today projects have to wrap the CLI in a repo: local hook (via npx or a system install) to run it before a commit. This one small file lets them consume it the standard way, pinned by rev, with pre-commit managing the install.

The hook runs the existing bin over staged Markdown files and formats their tables in place.

[echoix]

Looks right, from what I see when I use pre-commit hooks

Cc @nvuillam