Pre-commit support

Would be nice with support and guide to use Harper with [`pre-commit` tool](https://pre-commit.com/) just like [`typos` CLI tool do](https://github.com/crate-ci/typos/blob/master/docs/pre-commit.md)

Start by reading the pre-commit documentation and the linked typos pre-commit guide, then inspect Harper's CLI entry point to understand how an integration would invoke it. Done means Harper works as a pre-commit hook and the repository includes a guide showing how to configure and use it.

Written by the indexing model from the issue text.