docs: add a "rules" reference page that lists every rule with rationale + suggested fix

[depmedicdev-byte]

Background

ci-doctor ships 16 rules. The README lists them in a table but the
rationale and suggested fix are scattered.

What we want

A single docs/rules.md that, for each rule:

• ID (e.g. unpinned-action)
• Severity (error / warn / info)
• One-paragraph rationale (why this is a real problem)
• Bad example (5-line YAML)
• Good example (5-line YAML)
• Link back to the source file in src/rules/

The same content can be templated from the existing rule metadata; you
shouldn't need to rewrite the rule modules. A small Node script that
walks src/rules/*.js, reads the exported description /
severity, and renders Markdown is enough.

Acceptance

• New file docs/rules.md is generated and checked in
• A script tools/build-rules-doc.mjs regenerates it
• README links to docs/rules.md
• npm test still passes

Estimate

~1 hour for someone new to the repo.

This is a great first contribution; happy to review the PR same-day.

[snakefood3232]

I see you need a docs/rules.md that outlines each rule with rationale and examples. I'd handle this by writing a Node script to extract metadata from src/rules/*.js and generate the markdown file as specified. I can have a PR up in about 3 hours. I've built similar automated documentation tools in the past and can ensure everything integrates smoothly with your existing setup.