docs: polish README and relax engines to Node 20

[johnxie]

Summary

• GitHub About already filled (description, npm homepage, topics) — not in this PR.
• README first screenful: npm/CI/license badges, credit @lxcid, sibling link to temporal-parser.
• Honest “use WHATWG URL unless you need a lossless AST / host-path / no-scheme parse” table.
• LLM credit moved to CONTRIBUTING.
• engines.node >=22 → >=20. CI matrix adds 20.x. Stays 0.x (URI Template still open). No parser or API changes.
• Changeset for 0.2.0. Merging this PR lets the changesets bot open chore: version packages; merging that publishes to npm.

Test plan

• npm test — 166 passed locally
• npm run build — ESM + CJS + types
• CI green on 20.x, 22.x, 24.x
• After merge: version PR opens, then npm shows 0.2.0 with the new README

Made with Cursor

[Copilot]

🟢 Approval recommended

The documentation, package metadata, CI matrix, and changeset are consistent and introduce no unresolved correctness issues.

Pull request overview

Polishes project documentation and expands supported Node.js versions to Node 20.

Changes:

• Adds badges, attribution, related-project links, and usage guidance.
• Moves development attribution to the contributing guide.
• Adds Node 20 support to package metadata, CI, and release notes.

File summaries

File	Description
README.md	Improves introductory documentation and guidance.
CONTRIBUTING.md	Adds development attribution.
package.json	Lowers the Node.js minimum to 20.
package-lock.json	Synchronizes package engine metadata.
.github/workflows/ci.yml	Tests Node.js 20, 22, and 24.
.changeset/node20-and-docs.md	Records the minor release changes.

Review details

• Files reviewed: 5/6 changed files
• Comments generated: 0
• Review effort level: Balanced

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